STATE  GEOLOGICAL  SURVEY 


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GEOLOGICAL  SURVEY 


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ILLINOIS  STATE  GEOLOGICAL  SURVEY 


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ILLINOIS 


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STATE  GEOLOGICAL  SURVEY. 


BULLETIN  No.  7. 


Physical  Geography  of  the  Evanston 
Waukegan  Region 


BY 


Wallace  W.  Atwood  and  James  Walter  Goldthwait 


Urbana 

University  of  Illinois 

1908 


Springfield    III.  : 
Phillips  Bros.,  State  Printers. 

1908. 


TWAOEMrearrCOUNCIL  >  1  6  7 


551 

a.  5- 


STATE  GEOLOGICAL  COMMISSION. 


Governor  C.  S.  Deneen,  Chairman. 
Professor  T.  C.  Chamberlin,   Vice -Chairman. 
President  Edmund  J.  James,  Secretary. 


H.  Foster  Bain,  Director. 

R.  D.  Salisbury,  Consulting  Geologist,  in  charge  of  the  preparation 
of  Educational  Bulletins. 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://archive.org/details/physicalgeograph07atwo 


CONTENTS. 


Page. 

List    of    Illustrations VII 

Letter    of    Transmittal ! IX 

General  Geographic  Features,  by  W.  W.  Atwood 1 

Location  and   extent  of  area 1 

Upland   area 2 

Shore    line 3 

Lake    plain 3 

Drainage     3 

Geological  Formations,  by  W.  W.  Atwood 4 

General    characteristics 4 

Nature    of    materials 4 

Bedrock   surface  beneath   the   drift 4 

Structure     5 

Sources  of  materials 5 

Origin  and  work  of  continental  glaciers 6 

Formation  of  an  ice  sheet 6 

The   North  American   ice    sheet 9 

Work   of  glacier   ice 10 

Erosive    work 10 

Deposition   by    ice 13 

Direction    of    movement 16 

Effect  of  topography  on  movement 17 

Glacial     deposits 17 

General     characteristics 17 

Ground     moraine 20 

Distribution     20 

Constitution     : 21 

Topography     23 

Terminal    moraines 23 

Formation     23 

Topography     24 

Stratified     drift 24 

Contrast  between  glaciated   and   unglaciated   areas 26 

Present  Shore   Line,   by  J.   W.   Goldthwait 28 

Evolution   seen   in   shore   line    topography 28 

Geological  agents  at  work  along  shore  lines 29 

Waves     29 

Undertow     31 

Shore    current 32 

Development   of   coastal    topography 32 

Changes  in  profile 32 

The  sea  cliff 33 

The    beach    ridge 35 

The    barrier 36 

Changes  in  horizontal    configuration 38 


VI 

Contents — Concluded. 

Page. 

Spits,   bars   and   hooks 38 

Dunes     44 

The  shore  cycle , . . . .  45 

The    north    shore 47 

General    aspects 47 

The   ten-fathom   terrace 48 

The  coastal  topography — Rogers  Park  to  Winnetka 50 

Winnetka  to  Waukegan 51 

Waukegan  to  the  State  line 52 

Mature   condition   of  the  shore  line 53 

Records  of  the  Extinct  Lakes,  by  J.   W.   Goldthwait 54 

Introduction    54 

Lake    Chicago 55 

Glenwood    stage , 55 

Glenwood  shores  in   the   Evanston  district 56 

Glenwood  beaches  in  the  Waukegan   district 58 

Change  from  the  Glenwood  to  the  Calumet  stage 60 

Calumet    stage 61 

Calumet  shores  in  the  Evanston  district 61 

Calumet  beach  In  the  Waukegan  district 63 

Interval  between  the  Calumet  and  Toleston  stages 63 

Lake  Algonquin,  the  low  water  stage  and  the  Nipissing  great  lakes 64 

The    Toleston    beaches 65 

Lower  Toleston  bluff  and  shore  terrace  in  the  Waukegan  district 68 

Effects   of  recent  fluctuations   in  lake   level 68 

The  Development  of  the  Ravines,  by  W.  W.  Atwood 69 

Morainic  surface  as  left  by  the  ice 69 

Origin   of  a  gully 69 

The  course  of  a  valley 70 

Tributary    valleys 70 

How  a  valley  gets  a  stream 71 

Limits  of  a   valley 72 

A   cycle   of   erosion 73 

Base-level    plains   and    peneplains 75 

Characteristics  of  valleys  at  various  stages  of  development 76 

Transportation    and    deposition 79 

Topographic  forms  resulting  from  stream  deposition 79 

Rejuvenation    of    streams 80 

The  influence  of  the  changes  in  the  level  of  Lake  Michigan  on  valley  develop- 
ment   81 

Underground  water,  by  W.  W.  Atwood 85 

Shallow   ground   water 85 

Artesian     wells 85 

Geographic  Conditions  and   Settlement,  by  W.  W.  Atwood 89 

History     89 

Location  of  roads 89 

Towns    and    villages 90 

Soil  and   sub-soil 91 

Farms 91 

Suburban   and    summer   homes 92 

Former   village   of   St.   Johns 92 

Economic  uses  of  the  glacial  ■  material 92 

Rainfall 93 


APPENDIX. 

A.  Bibliography > 94 

B.  Field    Trips 95 


VII 


LIST  OF  ILLUSTRATIONS. 


PLATES. 

Page. 

Plate     I.      Fig.  A.  Glaciated  stones  showing  both  form  and  striae 17 

B.  Limestone  boulder  in  Pettibone  Creek,  North  Chicago 

C.  Igneous  boulder  at  Northwestern  Railway  station,    Waukegan 

II.  Fig.  A.  Abandoned  clay  pit  near  Fort  Sheridan 23 

B.  Sketch  of  ground  moraine  topography 

C.  Sketch  of  terminal  moraine  topography 

III.  Fig.  A.  Receding  cliff  at  Grosse  Point 33 

B.  Sand  dunes  at  Rogers  Park 

IV.  Fig.  A.  Lake  cliff  and  beach  near  Fort  Sheridan 34 

B.  Lake  cliff  at  Racine,   Wisconsin 

V.  Fig.  A.  Pier  and  beach  near  county  line 38 

B.  Bar  at  mouth  of  ravine  near  county  line 

VI.  Map  of  old  shore  lines  of  the  Evanston  district 56 

VII.  Fig.  A.  Lower  Toleston  bluff  and  beach  ridge 65 

B.  Ancient  beach  ridge  in  Evanston 

VIII.  Fig.  A.  Morainic  upland  descending  to  lake  shore 69 

B.  Young  valleys 

IX.  Fig.  A.  Same  valleys  as  shown  in  Plate  VIII 74 

B/  A  later  stage  of  development 

X.  Fig.  A.  North  Fork  Pettibone  Creek,  North  Chicago 77 

B.  A  broad,  open  valley  north  of  Kenosha 

XI.  Erosion  features  near  Highwood 79 

XII.  Mouth  of  Pettibone  Creek,  North  Chicago 82 

XIII.  Fig.  A.  Little  Fort  Creek  in  the  western  portio  n  of  Waukegan 84 

B.  Glacial  boulders  used  in  building 

XIV.  Fig.  A.  A  truck  farm  near  Rogers  Park 90 

B.  The  site  of  the  town  of  St.  Johns 


FIGURES  IN  TEXT. 

Figure  Page. 

1.  Index    map 2 

2.  Diagrammatic  cross-section  of  a  field  of  ice  and  snow 7 

3.  Map  of  area  covered  by  the  North  American  ice  sheet  at  its  maximum  exten- 

sion             9 


VIII 


List  of  Illustrations — Concluded. 


Figure  PAGE. 

4.  A  hill  before  the  ice  passes  over  it 12 

5.  The  same  hill  after  it  has  been  eroded  by  the  ice 12 

6.  Diagram  showing  the  effect  on  a  valley  of  ice  moving  transversely  across  it  12 

7.  Diagram  showing  ice  moving  across  a  valley.  / 13 

8.  Diagram  showing  the  relation  of  the  drift  to  the  underlying  rock  where  the 

drift  is  thick 15 

9.  The  same  where  the  drift  is  relatively  thin 15 

10.  Stratified  drift  at  Winthrop   Harbor 25 

11.  Drainage  in   the  drif  tless  area .  . 26 

12.  Drainage   in  a  glaciated   area '  26 

13.  Diagram  showing  the  relation  of  residual  soil  to  the  underlying  rock 27 

14.  Diagram  showing  the  movement  of  particles  in  a  wave 29 

15.  Series  of  particles  in  their  orbits.     Diff.   of  phase  45° 30 

16.  Same  as  Fig.  15,  but  with  the  diff.  of  phase  90° 30 

17.  Same  as  Fig.   15,  but  with  the  amplitude  doubled 30 

18.  Condition  for  breakers — wave   shortened  and   raised 30 

19.  Section  of  a  cliff  and  wave-cut  terrace 33 

20.  Section  of  a  cut  and  built  terrace 34 

21.  Section   of   a   beach 35 

22.  Sections   of   a    retreating   barrier 37 

23.  Map  of  New  Jersey 38 

24.  Map  of  a  part  of  Long  Island 39 

25.  Sketch  map  of  a  bay,  enclosed  by  overlapping  bars 40 

26.  Sketch  map  of  a  hooked  spit 41 

27.  Map  of  Rockaway  beach 42 

28.  Map   of   Sandy   Hook 43 

29.  Section  showing  how  a  deeply  submerged  terrace  may  develop 50 

30.  Map  of  the  Great  Lake  region  in  the  late  Wisconsin  stage  of  glaciation 55 

31.  Map  of  the  ice  front  lakes  at  the  time  of  the  Pt.  Huron  moraine 56 

32.  Map  of  the  old  shore  lines  between  Waukegan  and  State  line 59 

33.  Diagram    to   explain    "stoping" 61 

34.  Map    of    Lake    Algonquin 64 

35.  Map  of  the  Great  Lakes  at  the  low  water  stage 67 

36.  Map  of  the  Nipissing  Great  Lakes 67 

37.  Diagram  illustrating  the  relation  of  ground  water  to  streams 71 

38.  Diagram   illustrating  the   shifting  of  divides 73 

39.  Diagram  showing  topography  at  the  various  stages  of  an  erosion  cycle 76 

40.  Diagrammatic  cross-section  of  a  young  valley 77 

41.  Diagrammatic   profile    of   a   young  valley ' 77 

42.  Diagrammatic  cross-section  of  a  valley  in  a  later  stage  of  development 77 

43.  The  same  at  a  still  later  stage 77 

44.  Topographic  map  of  a  part  of  the  North  Shore  near  Ravinia,  showing  several 

young    valleys 78 

45.  Diagram   illustrating  the   topographic   effect    of   rejuvenation   of  a   stream   by 

uplift     80 

46.  Normal  profile  of  a  valley  bottom '. 81 

47.  Profile  of  a  stream  rejuvenated  by  uplift. 81 

48.  Topographic  map  of  the  lower  portion  of  Pettibone  Creek 82 

49.  Topographic  sketch  map  of  one  of  the   head  waters   of  Dead   River  between 

Waukegan   and   Beach 83 

50.  Well   section   in    South   Evanston 86 

51.  Main  absorbing  areas  for  Potsdam  and  St.  Peters  formations 87 

52.  Map  of  southern  portion  of  Zion  City 90 


IX 


LETTER  OF  TRANSMITTAL. 


State  Geological  Survey,  University  of  Illinois. 

Urbana,  III.,  Oct.  25,  1907. 

Governor  C.  S.  Deneen,  Chairman  and  Members  of  the  Geological 

Commission: 

Gentlemen — I  submit  herewith  a  report  upon  the  physical  geo- 
graphy of  the  Evanston-Waukegan  region,  with  the  recommendation 
that  it  be  published  as  Bulletin  7  of  the  survey.  This  report  has  been 
prepared  under  the  direction  of  Professor  R.  D.  Salisbury  of  the  Uni- 
versity of  Chicago,  consulting  geologist  of  this  survey.  It  forms  the 
first  of  a  series  now  in  preparation  of  "Educational- Bulletins."  Tftese 
have  been  called  educational  because  their  purpose  is  to  put  useful 
information  concerning  the  geology  and  geography  of  the  State,  or 
some  parts  of  it,  before  those  who  are  not  special  students  of  these 
sciences.  More  particularly,  their  purpose  is  to  put  into  available 
form  such  knowledge  as  will  help  those  who  are  not  geologists  in 
understanding  the  common  phenomena  of  their  own  regions.  The 
bulletins  are  therefore  intended  to  serve  the  citizens  at  large,  rather 
than  special  students  of  geology,  or  special  industries  of  the  State 
which  depend,  directly  or  indirectly  upon  the  mineral  resources. 
Other  and  more  technical  publications  serve  this  latter  purpose. 

Two  classes  of  people  are  kept  especially  in  mind  in  the  prepara- 
tion of  these  bulletins.  These  are:  (1)  Intelligent  citizens  whose 
attention,  for  one  reason  or  another,  has  never  been  directed  to  geo- 
logy. Among  such  citizens  there  are  always  some  who  are  interested 
in  understanding  their  home  regions ;  and  through  the  understanding 
of  one  region  the  general  principles  of  geology  may  be  grasped,  much 
more  easilv.  The  knowledge  thus  acquired  may  be  a  source  of 
much  satisfaction  to  those  who  possess  it.  Furthermore,  there  is  al- 
ways the  possibility  that  occasion  may  arise  in  the  future  when  the 
information  can  be  turned  to  account  in  economic  ways.  (2) 
Teachers  of  physical  geography  and  geology.  These  sciences  are  now 
taught  somewhat  generally  in  high  schools,  and  might  be  pursued 
with  great  ■  advantage  much  more  widely  than  now  in  the  country 
schools.  According  to  the  improved  methods  of  study  at  the  present 
time,  it  is  essential  that  the  subjects  studied  be  so  illustrated  and  ap- 
plied that  the  kuowledge  acquired  becomes  a  part  of  the  student's  per- 
manent equipment.  His  study  of  physical  geographv  fails  of  its  full 
purpose  unless  it  puts  him  into  possession  of  the  ability  to  interpret 

—13    G 


the  surface  of  the  land  as  he  travels  to  and  fro  in  after  life.  The 
best  way  to  acquire  this  ability  appears  to  be  to  make  application  of 
principles  studied  in  the  school  to  the  phenomena  of  the  region  in 
which  the  school  is  located.  Many  of  the  principles  of  physical  geo- 
graphy and  geology  are  illustrated  within  easy  reach  of  most  of  the 
schools  in  the  State. 

The  second  purpose  of  those  bulletins,  therefore,  is  to  put  the 
schools  of  the  various  parts  of  the  State  into  possession  of  a  general 
account  of  the  principal  geographic  and  geological  features  of  their  re- 
gions, which  may  be  used  as  a  sort  of  field  book.  This  field  study  in 
physical  geography  serves  the  same  purpose  as  laboratory  work  in 
physics  and  chemistry,  in  connection  with  those  subjects. 

It  will  be  long  before  all  the  important  regions  of  the  State  can  be 
covered  in  this  way.  In  the  choice  of  areas  selected  for  early  treat- 
ment, three  considerations  have  controlled.  These  are  the  following: 
(i).  Areas  of  great  inherent  interest  have  taken  precedence  over 
those  not  so  favored.  (2).  Areas  of  which  topographic  maps  have 
been  made  take  precedence  over  those  not  so  mapped;  and  (3)  areas 
where  the  bulletins  are  likely  to  be  used,  again  have  precedence.  Topo- 
graphic maps  have  as  yet  been  made  over  but  a  relatively  small  por- 
tion of  the  State.  Fortunately  the  lake  shore  from  Chicago  north- 
ward has  now  been  mapped,  the  Waukegan  quadrangle,  immediately 
north  of  the  Highwood  and  extending  to  the  State  line  having  just 
been  completed. 

This  area,  one  of  exceptional  and  varied  interest  from  the  point  of 
view  of  physical  geography,  was  chosen  as  the  first  to  be  reported  on. 
Dr.  Wallace  W.  Atwood  of  the  University  of  Chicago,  and  Dr.  James 
Walter  Goldthwait  of  Northwestern  University,  already  thoroughly 
familiar  with  the  region,  collaborated  in  the  preparation  of  the  accom- 
panying report.  It  is  hoped  that  the  material  here  brought  together 
will  stimulate  the  interest  not  only  of  the  citizens  and  students  of  the 
area,  but  that  it  may  also  enrich  the  teaching  of  physical  geography 
throughout  the  State.  The  clear  description  of  the  action  of  the 
continental  ice  sheet  which  once  covered  the  region,  the  fascinating" 
history  of  Lake  Michigan,  and  finally  the  analyses  of  the  development 
of  stream  courses  in  the  area  should  be  of  general  interest.  Inci- 
dentally the  discussion  of  the  water  resources  of  the  area  is  of  practi- 
cal importance  to  all  residents  of  this  thickly  populated  prea. 

The  survey  is  under  great  obligations  to  Professor  Salisburv  and 
the  authors  of  this  report  for  its  preparation.  Acknowledgments 
should  also  be  made  to  the  U.  S.  Geological  Survev  for  the  nse  of 
figures  3  and  13,  and  to  Director  E.  A.  Birge  of  the  Wisconsin  Geolo- 
gical and  Natural  History  Survey  for  the  use  of  figures  11  and  12; 
fig.  A,  plate  I :  fig.  ?>,  plate  VIII  and  fig.  A  and  B,  plate  IX. 

Others  similar  educational  bulletins  are  being  prepared  and  will  be 
offered  for  publication  as  rapidly  as  circumstances  will  permit. 

"Respectfully, 

H.  Foster  Bain, 

Director. 


PHYSICAL     GEOGRAPHY    OF     THE     EVANSTON- 
WAUKEGAN     REGION. 

By  Wallace  W.  Atwood  and  James  Walter  Goldthwait. 


GENERAL  GEOGRAPHIC  FEATURES. 

(BY    W.    W.    ATWOOD.  ) 

Location  and  Extent  of  Area — The  area  with  which  this  report  is 
concerned  lies  north  of  Chicago,  and  extends  northward  to  the  Illi- 
nois-Wisconsin line.  Its  eastern  boundary  is  the  shore  line  of  Lake 
Michigan,  and  its  western  margin,  the  DesPlaines  river  (Fig.  i).  It 
is  a  little  over  30  miles  long  and  varies  in  width  from  5  to  10  miles. 
Its  area  is  about  250  square  miles.  Of  this  area,  the  portion  immed- 
iately adjoining  Lake  Michigan  has  attracted  most  attention.  It  is  a 
beautiful  suburban-home  district  and  a  region  of  considerable  scien- 
tific and  educational  interest.  Each  year  hundreds,  if  not  thousands 
of  students  visit  points  of  special  interest  along  this  shore.  It  is  not 
uncommon  for  special  trains  to  be  chartered  and  entire  schools  to  be 
taken  on  educational  excursions  to  this  "North  Shore"  region.  The 
portion  near  the  lake  may  be  regarded  as  a  great  physiographic  labor- 
atory. 

The  "Chicago  region"  is  interpreted  as  the  area  mapped  in  the 
Chicago  folio  of  the  United  States  Geological  Survey,  and  includes 
the  area  covered  by  the  Calumet,  Des  Plaines,  Riverside  and  Chicago 
sheets,  of  the  U.  S.  Geological  Survey.  The  north  boundary  of  the 
Riverside  and  Chicago  quadrangles,*  latitude  42  degrees,  is  the  south- 
ern boundary  of  the  area  here  under  discussion.  The  Evanston  and 
Highwood  quadrangles  are  located  just  north  of  the  Chicago  region 
and  included  within  the  region  here  concerned  (Fig.  1). 

The  quadrangle  adjoining  the  Highwood  on  the  north,  includes 
the  Waukegan  region  and  is  known  as  the  Waukegan  quadrangle. 
This  map  will  soon  be  ready  for  distribution. 


*  A  quadrangle  is  the  area  represented  on  one  sheet  of  the  U.  S.  Geological  Survey  topo- 
graphic map.  Topographic  maps  of  the  quadrangles  included  in  the  Chicago  folio  and  of  the 
Evanston,  Waukegan  and  Highwood  regions  may  be  purchased  of  the  director  of  the  U.  S. 
Geological  Survey,  Washington,  D.  C,  at  5  cents  per  copy  or  $3.00  per  hundred.  The  Evanston, 
Waukegan  and  Highland  sheets  should  he  used  in  connection  with  this  report,  and  the  Chicago 
folio,  also  to  be  had  of  the  U.  S.  Geological  Survey,  will  also  be  instructive. 


THE   EVANSTON-WAUKEGAN    REGION. 


[BULL.  7 


Fig.  1.  General  map  showing  location  and  extent  of  the  Evanston-Waukegan  region,  the 
quadrangles  for  which  topographic  maps  are  available,  and  the  chief  points  mentioned  in  the 
report. 

The  general  geographic  features  of  the  region  are:  (i)  the  mor- 
aine plain  or  rolling  upland,  (2)  the  present  shore,  (3)  the  lake  plain 
with  associated  beach  ridges,  and  (4)  the  ravines. 

Upland  Area — The  larger  part  of  the  area  consists  of  rolling  up- 
land more  than  60  feet  above  the  level  of  the  lake.  Going  northward 
from  Chicago  the  Northwestern  railroad  bed  becomes  noticeably 
higher  a  few  rods  south  of  the  station  at  Winnetka,  and  before  the 
station  is  reached  the  road  bed  has  passed  from  the  lower,  flatter  plain 
to  the  south,  to  the  rolling  upland  farther  north.  Northward  from 
Winnetka  the  railroad  remains  on  the  upland  to  Waukegan,  where  it 
descends  again  to  the  lake  plain.    West  of  the  railroad,  the  undulating 


atwood.]  GENERAL    GEOGRAPHIC    FEATURES.  6 

surface  of  the  upland  contains  many  swamps,  ponds  and  other  de- 
pressions without  outlets.  The  topography  is  such  as  is  common  to 
glacial  drift  and  it  will  be  fully  discussed  later  in  the  report. 

Shore  Line — The  modern  lake  cliff  extends  from  the  southern  mar- 
gin of  Waukegan  southward  a  little  beyond  Evanston.  It  varies  in 
height  up  to  80  feet,  and  at  places  is  almost  vertical.  At  the  base  of 
the  cliff,  is  the  modern  beach.  Over  the  beach  zone,  the  waves  and 
undertow  work  the  sands  and  gravels  back  and  forth.  When  strong 
winds  blow  from  the  east  or  northeast,  the  waves  reach,  at  certain 
places,  to  the  base  of  the  cliff  and  thus  submerge  the  entire  beach. 
As  the  winds  die  down  or  set  in  from  the  west,  the  lake  waters  fall 
or  are  blown  eastward,  uncovering  a  wide  beach.  Normally  there  is 
a  belt  50  to  100  feet  wide  bordering  the  water,  and  rising  a  few  feet 
above  the  level  of  the  lake. 

Lake  Plain — This  appears  in  the  southeast  and  northeast  corners  of 
the  area.  Evanston,  Wilmette,  Kenilworth  and  a  portion  of  Win- 
netka  are  located  on  the  plain  at  the  southeast.  The  lower  or  manu- 
facturing portion  of  Waukegan,  most  of  Zion  City,  and  all  of  Beach, 
Camp  Logan  and  Winthrop  Harbor  are  on  the  lake  plain  at  the 
northeast  corner  of  the  area.  The  beaches  associated  with  the  plain 
are  low,  even-crested  ridges  of  sand  and  gravel  built  upon  the  plain 
and  running  approximately  parallel  to  the  present  shore  line  of  the 
lake.  At  the  landward  margin  of  the  lake  plain  there  is  usually  a 
distinct  rise  of  10  to  60  feet  to  the  upland.  This  is  well  shown  at 
Winnetka  and  at  Waukegan.  In  the  southern  portion  of  the  area, 
in  the  vicinity  of  the  Chicago  river,  the  change  from  the  plain  to  the 
upland  is  not  abrupt,  and  the  margin  of  the  plain  is  not  easily  recog- 
nized. 

East  of  the  Northwestern  railroad  the  upland  belt  has  been  dis- 
sected by  numerous  intermittent  or  wet- weather  streams.  The  gullies 
and  ravines  which  have  resulted  from  the  work  of  such  streams  add 
much  to  the  roughness  of  the  topography,  and  much  to  the  scenic  at- 
tractiveness of  the  region. 

Drainage — The  drainage  of  the  western  portion  of  the  area  joins 
the  Des  Plaines  river,  and  thence  by  way  of  the  Illinois  and  Missis- 
sippi enters  the  Gulf  of  Mexico.  The  central  portion  is  drained  by  the 
north  branch  of  the  Chicago  river.  The  waters  following  this  route 
are  now  diverted  up  the  south  branch  of  the  Chicago  river  into  the 
Chicago  drainage  canal,  and  thence  into  the  Des  Plaines.  The  eastern 
border  of  the  area  is  drained  by  numerous  short  streams  into  Lake 
Michigan.  From  the  lake  these  waters  may  go  in  part  southward 
through  the  Chicago  outlet,  and  in  part  northward  to  the  Atlantic 
ocean  by  way  of  the  great  lakes  and  the  St.  Lawrence  river. 


THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 


THE  GEOLOGICAL  FORMATIONS. 
(by  w.  w.  atwood.) 

Nature  of  Materials — General  Characteristics — All  of  the  rock 
material  within  the  Evanston-Waukegan  region  is  glacial  drift,  com- 
posed of  clay,  sand,  gravel  and  bowlders.  A  part  of  this  material  has 
been  re-worked  by  rivers,  winds,  or  waves  since  the  ice  retreated. 
Such  material  is  stratified,  and  is  sometimes  called  modified  drift,  and 
will  receive  special  attention  later.  The  portion  that  may  be  consid- 
ered as  unmodified,  or  but  slightly  modified  glacial  drift,  underlies  the 
lake  plain  and  the  entire  upland.  It  is  well  exposed  in  the  lake  cliff, 
in  many  of  the  ravines,  and  in  most  all  excavations.  Road  cuttings, 
sewer  or  water-pipe  excavations,  and  all  deep  basements  or  cellars, 
when  being  excavated,  afford  excellent  opportunities  for  studying 
this  formation.  The  material  grades  from  fine  silt,  to  huge  bowlders 
10  or  12  feet  in  diameter.  Between  these  extremes  there  are  various 
grades  of  sand,  gravel  and  cobble-stones.  The  great  mass  of  the  ma- 
terial is  firmer  than  sand,  and  may  be  classed  as  clay,  or  better  as 
stony  clay. 

In  addition  to  the  variation  in  size,  there  is  variation  in  the  kinds 
of  rocks  found  in  the  drift.  Almost  any  exposure  in  the  region  will 
yield  four  or  five  varieties,  while  on  the  beach  it  is  easy  to  find  20  or 
more  different  kinds  of  stones. 

The  shapes  of  the  pebbles  and  bowlders  in  the  unstratified  drift  are 
not  like  those  of  stream  or  shore  pebbles.  Instead  of  having  smoothly 
rounded  forms,  the  stones  of  the  drift  are  commonly  sub-angular, 
with  numerous  flat  faces,  or  facets.  The  facets  usually  show  polish- 
ing, parallel  grooving,  and  scratching,  as  though  smoothed  and 
striated  while  being  held  firmly  in  one  position,  and  moved  over  a 
hard  surface  (Plate  I,  Fig.  A). 

Bed-rock  Surface  Beneath  the  Drift — Nowhere  within  the  Evans- 
ton-Waukegan region,  so  far  as  the  authors  are  aware,  does  the  bed- 
rock underlying  the  glacial  drift  appear  at  the  surface.  The  nearest 
exposures  of  the  rock  that  underlies  this  area  are  within  the  Chicago 
region.  When  these  exposures  are  examined  they  are  usually  found 
to  be  smoothed  and  polished,  and  marked  by  gooves  and  scratches 
similar  to  those  upon  the  pebbles  and  bowlders  in  the  drift.  The 
scratches  on  the  bed-rock  are  usually  parallel  at  any  one  locality, 
but  when  examined  at  widely  separated  localities  within  the  Chicago 
region,  they  are  found  to  vary  in  direction  from  20  degrees  to  45 
degrees  south  of  west. 


atwood.]  THE   GEOLOGICAL    FORMATIONS.  O 

Structure — Any  good  section  of  the  glacial  drift  along  the  north 
shore  shows  that  most  of  the  material  is  unstratified.  In  other  words, 
the  sand,  clay,  gravel  and  bowlders  are  at  most  places  intimately  in- 
termingled, and  show  no  signs  of  assortment.  At  a  few  places,  most 
noticeably  in  the  lake  cliff  just  south  of  Pettibone  creek,  at  North 
Chicago,  the  glacial  material  is  assorted.  Here  sands  and  gravels  of 
a  given  size  are  arranged  in  distinct  lavers.  Such  material  was  evi- 
dently deposited  by  water,  and  presumably  by  water  associated  with 
the  melting  of  the  glacial  ice  which  once  covered  the  region. 

The  unassorted  or  unstratified  glacial  drift  was  deposited  by  the 
ice  itself,  and  it  now  lies  as  the  ice  left  it.  As  the  ice  melted  or  for 
any  reason  gave  up  the  rock  material  it  was  carrying,  such  material 
was  left  on  the  surface  beneath.  In  this  process,  there  was  no  possi- 
bility of  getting  the  sands  or  pebbles  of  a  common  size  together. 
The  material,  large  or  small,  which  was  left  at  one  time,  took  its 
place  on  that  which  had  been  last  deposited  in  the  same  place.  Un- 
stratified glacial  drift  is  known  as  till. 

The  various  phenomena  of  the  drift  of  the  region  give  unmistakable 
evidence  of  that  agent  that  brought  that  material.  The  physical  and 
structural  features  of  the  material  are  identical  with  those  of  the 
material  carried  or  but  recently  deposited  by  the  glaciers  of  today. 
The  markings  of  the  bed-rock  surface,  exposed  in  neighboring  re- 
gions to  the  north  and  south,  and  underlying  the  same  great  sheet  or 
drift  that  occupied  the  Evanston-Waukegan  region,  are  identical 
with  the  markings  of  the  bed-rock  surfaces  under  living  glaciers, 
and  of  rock  surfaces  from  which  glaciers  have  but  recently  retreated. 
Furthermore,  the  shapes  and  markings  of  the  stones  in  the  drift  are 
identical  with  the  shapes  and  markings  of  stones  underneath  and  in 
the  base  of  the  glaciers  of  today.  The  drift  is,  therefore,  of  glacial 
origin. 

Sources  of  the  Drift  Materials — The  clay  matrix  of  the  drift  is 
highly  calcareous,  and  was  derived  largely  from  limestone  and  cal- 
careous shale  by  grinding  and  crushing.  The  limestone  was  pre- 
sumably the  underlying  Niagara  formation  which  aooears  at  several 
places  in  Chicago,  and  is  reached  in  the  deep  wells  of  the  Evanston- 
Waukegan  region.  This  formation  extends  far  to  the  northeast. 
Of  the  stones  of  the  drift  in  this  region,  about  90  per  cent  are  from 
the  Niagara  limestone,  while  the  remaining  10  per  cent  are  of  sand- 
stone, shales  and  crystalline  rock,  foreign  to  Illinois.  From  the  di- 
rection of  glacial  striae  on  bed-rock  in  Chicago  and  in  southern  Wis- 
consin, it  is  known  that  the  glacier  that  brought  the  drift  material 
to  this  region,  moved  southward  in  the  basin  of  Lake  Michigan  and 
spread  southward  over  the  area  bordering  the  lake  on  the  west.  If 
the  course  of  the  ice  be  retraced,  it  is  found  that  the  sandstones  and 
crystalline  rocks  in  the  drift  of  this  region  must  have  come  at  least 
500  miles,  and  may  have  traveled  much  farther.  Such  rocks  occur, 
in  place,  about  the  eastern  part  of  Lake  Superior,  northern  Lake 
Huron,  and  further  northward.  The  glacier  that  reached  this  area 
was  therefore  not  local.  Furthermore,  drift  similar  to  that  in  the 
Evanston-Waukegan  region  covers  most  of  Illinois,  and  extends  over 


6  THE   EVANSTON-WAUKEGAN    REGION.  Ibdll   7 

most  of  the  northern  United  States  and  Canada.  The  drift  of  this 
region  is  therefore  a  part  of  a  great  sheet  of  drift  deposited  by  a  glacier 
of  continental  dimensions. 


Origin  and  Work  of  Continental  Glaciers.* 

the  formation  of  an  ice  sheet. 

To  clearly  understand  the  origin  of  the  drift,  and  the  methods  by 
which  it  attained  its  present  widespread  distribution,  it  is  necessary  to 
consider  some  elementary  facts  and  principles  concerning  the  forma- 
tion and  work  of  a  continental  glacier,  even  at  the  risk  of  repeating 
what  is  already  familiar. 

The  temperature  and  the  snow  fall  of  a  region  may  stand  in  such  a 
relation  to  each  other  that  the  summers'  heat  may  barely  suffice  to 
melt  the  winters'  snow.  If  under  these  circumstances  the  annual  tem- 
perature were  to  be  reduced,  or  the  fall  of  snow  increased,  the  sum- 
mer's heat  would  fail  to  melt  all  the  winter's  snow,  and  some  portion 
of  it  would  endure  through  the  summer,  and  through  successive  sum- 
mers, constituting  a  perennial  snow  field.  Were  this  process  once  in- 
augurated, the  depth  of  the  snow  would  increase  from  year  to  year. 
The  area  of  the  snow  field  would  be  extended  at  the  same  time,  since 
the  snow  field  would  so  far  reduce  the  surrounding  temperature  as  to 
increase  the  proportion  of  the  annual  precipitation  which  fell  as  snow. 
In  the  course  of  time,  and  under  favorable  conditions,  the  area  of  the 
snow  field  would  attain  great  dimensions,  and  the  depth  of  the  snow 
would  become  very  great. 

As  in  the  case  of  existing  snow  fields,  the  lower  part  of  the  snow 
would  eventually  be  converted  into  ice.  Several  factors  would  con- 
spire to  this  end.  i.  The  pressure  of  the  overlying  snow  would  tend 
to  compress  the  lower  portion,  and  snow  rendered  sufficiently  com- 
pact by  compression  would  be  regarded  as  ice.  2.  Water  arising 
from  the  melting  of  the  surface  snow  by  the  summer's  heat  would 
percolate  through  the  superficial  layers  of  snow,  and,  freezing  below, 
take  the  form  of  ice.  3.  On  standing,  even  without  pressure  or  par- 
tial melting,  snow  appears  to  undergo  changes  of  crystallization 
which  render  it  more  compact.  In  these  and  perhaps  other  ways,  a 
snow  field  becomes  an  ice  field,  the  snow  being  restricted  to  its 
surface. 

Eventually  the  increase  in  the  depth  of  the  snow  and  ice  in  a  snow 
field  will  give  rise  to  new  phenomena.  Let  a  snow  and  ice  field  be 
assumed  in  which  the  depth  of  snow  and  ice  is  greatest  at  the  center, 
with  diminution  toward  its  edges.  The  field  of  snow,  if  resting  on  a 
level  base,  would  have#  some  such  cross-section  as  that  represented  in 
the  diagram,  Fig.  2. 


*  In  the  preparation  of  the  text  bearing-  on  the  principles  of  glaciation,  free  use  has  been 
made  of  material  in  Bull.  V.  Wisconsin  Geological  and  Natural  History  Survey,  Salisbury  and 
Atwood. 


A  I  W<X  I>. 


THE   GEOLOGICAL    FORMATIONS. 


Fig.  2.     Diagrammatic  cross-section  of  a  field  of  ice  and  snow  (c)  resting 
on  a  level  base  (a— b) 


When  the  thickness  of  the  ice  has  become  considerable,  it  is  evident 
that  the  pressure  upon  its  lower  and  marginal  parts  will  be  great. 
We  are  wont  to  think  of  ice  as  a  brittle  solid.  If  in  its  place  there 
were  some  plastic  substances  which  would  yield  to  pressure,  the 
weight  of  the  ice  would  cause  the  maginal  parts  to  extend  themselves 
in  all  directions  by  a  sort  of  flowing  motion. 

Under  great  pressure,  many  substances  which  otherwise  appear  to 
be  solid,  exhibit  the  characteristics  of  plastic  bodies.  Among  the  sub- 
stances exhibiting  this  property,  ice  is  perhaps  best  known.  Brittle 
and  resistent  as  it  seems,  it  may  yet  be  molded  into  almost  any  de- 
sirable form  is  subjected  to  sufficient  pressure,  steadily  applied  through 
long  intervals  of  time.  The  changes  of  form  thus  produced  in  ice  are 
brought  about  without  visible  fracture.  Concerning  the  exact  nature 
of  the  movement,  physicists  are  not  agreed,  but  the  result  appears  to 
be  essentially  such  as  would  be  brought  about  if  the  ice  were  capable 
of  flowing,  with  extreme  slowness,  under  great  pressure  continuously 
applied. 

In  the  assumed  ice  field,  there  are  the  conditions  for  great  pressure 
and  for  its  continuous  application.  If  the  ice  be  capable  of  moving 
as  a  plastic  body,  the  weight  of  the  ice  would  induce  gradual  movement 
outward  from  the'center  of  the  field,  so  that  the  area  surrounding  the 
region  where  the  snow  accumulated  would  gradually  be  encroached 
upon  by  the  spreading  of  the  ice.  Observation  shows  that  this  is  what 
takes  place  in  every  snow  field  of  sufficient  depth.  Motion  thus  brought 
about  is  glacier  motion,  and  ice  thus  moving  is  glacier  ice. 

Once  in  motion,  two  factors  would  determine  the  limit  to  which  the 
ice  would  extend  itself:  (I)  the  rate  at  which  it  advances:  (2)  the 
rate  at  which  the  advancing  edge  is  wasted.  The  rate  of  advance 
would  depend  upon  several  conditions,  one  of  which  in  all  cases,  would 
be  the  pressure  of  the  ice  which  started  and  which  perpetuates  the 
motion.  If  the  pressure  be  increased  the  ice  will  advance  more  rapidly, 
and  if  it  advances  -more  rapidly,  it  will  advance  farther  before  it  is 
melted.  Other  things  remaining  constant,  therefore,  increase  of  pres- 
sure will  cause  the  ice  sheet  to  extend  itself  farther  from  the  center 
of  motion.  Increase  of  snowfall  will  increase  the  pressure  of  the  snow 
and  ice  field  by  increasing  its  mass.  If,  therefore,  the  precipitation 
over  a  given  snow  field  be  increased  for  a  period  of  years,  the  ice 
sheet's  marginal  motion  will  be  accelerated,  and  its  area  enlarged.  A 
decrease  of  precipitation,  taken  in  connection  with  unchanged  wastage 
would  decrease  the  pressure  of  the  ice  and  retard  its  movement.  If, 
while  the  rate  of  advance  diminished,  the  rate  of  wastage  remained 
constant,  the  edge  of  the  ice  would  recede  and  the  snow  and  ice  field 
be  contracted. 


O  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

The  rate  at  which  the  edge  of  the  advancing  ice  is  wasted  depends 
largely  on  the  climate.  If,  while  the  rate  of  advance  remains  con- 
stant, the  climate  become  warmer,  melting  will  be  more  rapid,  and 
the  ratio  between  melting  and  advance  will  be  increased.  The  edge  of 
the  ice  will  therefore  recede.  The  same  result  will  follow  if,  while 
temperature  remains  constant,  the  atmosphere  becomes  drier,  since 
this  will  increase  wastage  by  evaporation.  Were  the  climate  to  be- 
come warmer  and  drier  at  the  same  time,  the  rate  of  recession  of  the 
ice  would  be  greater  than  if  but  one  of  these  changes  occurred. 

If,  on  the  other  hand,  the  temperature  over  and  about  the  ice-field 
be  lowered,  melting  will  be  diminished,  and  if  the  rate  of  movement 
be  constant,  the  edge  of  the  ice  will  advance  farther  than  under  the 
earlier  conditions  of  temperature,  since  it  has  more  time  to  advance 
before  it  is  melted.  An  increase  in  the  humidity  of  the  atmosphere, 
while  the  temperature  remains  constant,  will  produce  the  same  result, 
since  increased  humidity  of  the  atmosphere  diminishes  evaporation. 
A  decrease  of  temperature,  decreasing  the  melting,  and  an  increase  of 
humidity,  decreasing  the  evaporation,  would  cause  the  ice  to  advance 
farther  than  either  change  alone,  oince  both  changes  decrease  the 
wastage.  If,  at  the  same  time  that  conditions  so  change  as  to  increase 
the  rate  of  movement  of  the  ice,  climatic  conditions  so  change  as  to 
reduce  the  rate  of  waste,  the  advance  of  the  ice  before  it  is  melted  will 
be  greater  than  where  only  one  set  of  conditions  is  altered.  If,  instead 
of  favoring  advance,  the  two  series  of  conditions  conspire  to  cause  the 
ice  to  recede,  the  recession  will  likewise  be  greater  than  when  but  one 
set  of  conditions  is  favorable  thereto. 

Greenland  affords  an  example  of  the  conditions  here  described.  The 
large  part  of  the  half  million  or  more  square  miles  which  this  body  of 
land  is  estimated  to  contain,  is  covered  by  a  vast  sheet  of  snow  and  ice, 
thousands  of  feet  in  thickness.  In  this  field  of  snow  and  ice,  there  is 
continuous  though  slow  movement.  The  ice  creeps  slowly  toward  the 
borders  of  the  island,  advancing  until  it  reaches  a  position  where  the 
climate  is  such  as  to  waste  (melt  and  evaporate)  it  as  it  advances. 

The  edge  of  the  ice  does  not  remain  fixed  in  position.  There  is  rea- 
son to  believe  that  it  alternately  advances  and  retreats  as  the  ratio 
between  movement  and  waste  increases  or  decreases.  These  oscilla- 
tions in  position  are  doubtless  connected  with  climatic  changes.  When 
the  ice  edge  retreats,  it  may  be  because  the  waste  is  increased,  or  be- 
cause the  snowfall  is  decreased,  or  both.  In  any  case,  when  the  ice 
edge  recedes  from  the  coast,  it  tends  to  recede  until  its  edge  reaches 
a  position  where  the  melting  is  less  rapid  than  in  its  former  position, 
and  where  the  advance  is  counterbalanced  by  the  waste.  This  repre- 
sents a  condition  of  equilibrium  so  far  as  the  edge  of  the  ice  is  con- 
cerned, and  here  the  edge  of  the  ice  would  remain  so  long  as  the  con- 
ditions were  unchanged. 

When  for  a  period  of  years  the  rate  of  melting  of  the  ice  is  dimin- 
ished, or  the  snowfall  increased,  or  both,  the  ice  edge  advances  to  a  new 
line  where  melting  is  more  rapid  than  at  its  former  edge.  The  edge 
of  the  ice  would  tend  to  reach  a  position  where  waste  and  advance 
balance.  Here  its  advance  would  cease,  and  here  its  edge  would  re- 
main so  long  as  climatic  conditions  were  unchanged. 


ATWOOD.] 


THE   GEOLOGICAL    FORMATIONS. 


If  the  conditions  determining  melting  and  movement  be  continually 
changing,  the  ice  edge  will  not  find  a  position  of  equilibrium,  but  will 
advance  when  the  conditions  are  favorable  for  advance,  and  retreat 
when  the  conditions  are  reversed. 

Not  only  the  edge  of  the  ice  in  Greenland,  but  the  ends  of  existing 
mountain  glaciers  as  well,  are  subject  to  fluctuation,  and  are  delicate 
indices  of  variations  in  the  climate  of  the  regions  where  they  occur. 

The  North  American  Ice  Sheet — In  the  area  north  of  the  eastern 
part  of  the  United  States  and  in  another  west  of  Hudson  Bay  it  is 
believed  that  ice  sheets  similar  to  that  which  now  covers  Greenland 
began  to  accumulate  at  the  beginning  of  the  glacial  period.  From  these 
areas  as  centers,  the  ice  spread  in  all  directions,  partly  as  the  result 
of  accumulation,  and  partly  as  the  result  of  movement  induced  by  the 
weight  of  the  ice  itself. 


Fig.  3.    Map  of  area  covered  by  the  North  American  ice  sheet  of  the  glacial  epoch  at  its 
maximum  extension,  showing  the  approximate  southern  limit  of  glaciation,  the  three  main 


10  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

The  ice  sheets  spreading  from  these  centers  came  together  south  of 
Hudson's  bay,  and  invaded  the  territory  of  the  United  States  as  a 
single  sheet,  which,  at  the  time  of  its  greatest  development,  covered  a 
large  part  of  our  country  (Fig.  3),  its  area  being  known  by  the  extent 
of  the  drift  which  it  left  behind  when  it  was  melted.  In  the  east,  it 
buried  the  whole  of  New  England,  most  of  New  York,  and  the  north- 
ern part  of  New  Jersey  and  Pennsylvania.  Farther  west,  the  southern 
margin  of  the  ice  crossed  the  Ohio  river  in  the  vicinity  of  Cincinnati, 
and  pushed  out  over  the  uplands  a  few  miles  south  of  the  river.  In  In- 
diana, except  at  the  extreme  east,  its  margin  fell  considerably  short  of 
the  Ohio  ;  in  Illinois  it  reached  well  toward  that  river,  attaining  here  its 
most  southerly  latitude.  West  of  the  Mississippi,  the  line  which  marks 
the  limit  of  its  advance  curves  to  the  northward,  and  follows,  in  a 
general  way,  the  course  of  the  Missouri  river.  The  total  area  of  the 
North  America  ice  sheet,  at  the  time  of  its  maximum  development,  has 
been  estimated  to  have  been  about  4,000,000  square  miles,  or  about  ten 
times  the  estimated  area  of  the  present  ice-field  of  Greenland. 

Within  the  general  area  covered  by  the  ice,  there  is  an  area  of  sev- 
eral thousand  square  miles,  mainly  in  south-western  Wisconsin,  where 
there  is  no  drift.  The  ice,  for  some  reason,  failed  to  cover  this  drift- 
less  area  though  it  overwhelmed  the  territory  on  all  sides. 

The  Evanston-Waukegan  region  was  affected  by  the  ice  of  more 
than  one  glacial  epoch,  but  the  chief  results  now  observable  were  ef- 
fected during  the  last,  and  the  others  need  not  be  considered.  Figure 
30  shows  the  maximum  portion  of  ice  in  this  region  during  the  last 
glacial  epoch. 

WORK  OF  GLACIER  ICE. 

As  the  edge  of  an  ice  sheet,  or  as  the  end  of  a  glacier,  retreats,  the 
land  which  it  has  previously  covered  is  laid  bare,  and  the  effects  which 
the  passage  of  the  ice  produced  may  be  seen.  In  some  cases  one  may 
actually  go  back  a  short  distance  beneath  the  ice  now  in  motion,  and 
see  its  mode  of  work  and  the  results  it  is  effecting.  The  beds  of  living 
glaciers,  and  the  beds  which  glaciers  have  recently  abandoned  are 
found  to  present  identical  features.  Because  of  their  greater  accessi- 
bility, the  latter  offer  the  better  facilities  for  determining  the  effects  of 
glaciation. 

The  conspicuous  phenomena  of  abandoned  glacier  beds  fall  into  two 
classes,  (1)  those  which  pertain  to  the  bed  rock  over  which  the  ice 
moved,  and  (2)  those  which  pertain  to  the  drift  left  by  the  ice. 

Erosive  Work  of  the  Ice — Effect  on  Topography — The  leading  fea- 
tures of  the  rock  bed  over  which  glacier  ice  has  moved,  are  easily  rec- 
ognized. Its  surface  is  generally  smoothed  and  polished,  and  fre- 
quently marked  by  lines  (striae)  or  groves,  parallel  to  one  another. 
An  examination  of  the  bottom  of  an  active  glacier  discloses  the  method 
by  which  the  polishing  and  scoring  are  accomplished. 

The  lower  surface  of  the  ice  is  thickly  set  with  a  quantity  of  clay, 
sand,  and  stony  material  of  various  grades  of  coarseness.  These  earthy 
and  stony  materials  in  the  base  of  the  ice  are  the  tools  with  which  it 


atwood.1  THE   GEOLOGICAL    FORMATIONS.  11 

works.  Thus  armed,  the  glacier  ice  moved  slowly  forward,  resting 
down  upon  the  surfaces  over  which  it  passes  with  the  whole  weight  of 
its  mass,  and  the  grinding  action  between  the  stony  layer  at  the  base  of 
the  ice  and  the  rock  bed  over  which  it  moves,  is  effective.  If  the  mater- 
ial in  the  bottom  of  the  ice  be  fine,  like  clay,  the  rock  bed  is  polished. 
If  coarser  materials,  harder  than  the  bed-rock,  be  mingled  with  the  fine, 
the  rock  bed  of  the  glacier  will  be  scratched  as  well  as  polished.  If 
there  are  bowlders  in  the  bottom  of  the  ice  they  may  cut  grooves  or 
gorges  in  the  underlying  rock.  The  grooves  may  subsequently  be 
polished  by  the  passage  over  and  through  them  of  ice  carrying  clay  or 
other  fine,  earthy  matter. 

All  these  phases  of  rock  wear  may  be  seen  about  the  termini  of  re- 
ceding glaciers,  on  territory  which  they  have  but  recently  abandoned. 
There  can  thus  be  no  possible  doubt  as  to  the  origin  of  the  polishing, 
planing  and  scoring. 

There  are  other  peculiarities,  less  easily  defined,  which  characterize 
the  surface  of  glacier  beds.  The  wear  effected  is  not  confined  to  the 
mere  marking  of  the  surface  over  which  it  passes.  If  prominences  of 
rock  exist  in  its  path,  as  is  often  the  case,  they  oppose  the  movement  of 
the  ice,  and  receive  a  corresponding  measure  of  abrasion  from  it.  If 
they  be  sufficiently  resistant  they  may  force  the  ice  to  yield  by  passing 
over  or  around  them,  but  if  they  be  weak,  they  are  likely  to  be  des- 
troyed. 

As  the  ice  of  the  North  American  ice  sheet  advanced,  seemingly  more 
rigid  when  it  encountered  yielding  bodies,  and  more  yielding  when  it 
encountered  resistant  ones,  it  denuded  the  surface  of  its  loose  and  mov- 
able materials,  and  carried  them  forward.  This  accumulation  of  earthy 
and  stony  debris  in  the  bottom  of  the  ice,  gave  it  a  rough  and  grind- 
ing lower  surface,  which  enabled  it  to  abrade  the  land  over  which  it 
passed  much  more  effectively  than  ice  alone  could  have  done.  Every 
hill  and  every  mound  which  the  ice  encountered  contested  its  advance. 
Every  sufficiently  resistant  elevation  compelled  the  ice  to  pass  around 
or  over  it ;  but  even  in  these  cases  the  ice  left  its  marks  upon  the  sur- 
face to  which  it  yielded.  The  powerful  pressure  of  pure  ice,  which  is 
relatively  soft,  upon  firm  hills  of  rock,  which  are  relatively  hard,  would 
effect  little.  The  hills  would  wear  the  ice,  but  the  effect  of  the  ice  on 
the  hills  would  be  slight.  But  where  the  ice  is  supplied-  with  earthy 
and  stony  material  derived  from  the  rock  itself,  the  case  is  different. 
Under  these  conditions,  the  ice,  yielding  only  under  great  pressure  and 
as  little  as  may  be,  rubs  its  rock-shod  base  over  every  opposing  surface, 
and  with  greatest  severity  where  it  meets  with  greatest  resistance.  Its 
action  may  be  compared  to  that  of  a  huge  "flexible-rasp"  fitting  down 
snugly  over  hills  and  valleys  alike,  and  working  under  enormous  pres- 
sure. 

The  abrasion  effected  by  a  moving  body  of  ice  under  such  conditions 
would  be  great.  Every  inch  of  ice  advance  would  be  likely  to  be  at- 
tended by  loss  to  the  surface  of  any  obstacle  over  or  around  which  it 
is  compelled  to  move.  The  sharp  summits  of  the  hills,  and  all  the  an- 
gular rugosities  of  their  surfaces  would  be  filed  off,  and  the  hills 
smoothed  down  to  such  forms  as  will  offer  progressively  less  and  less 


12 


THE   EVANSTON-WAUKEGAN    REGION. 


Lbull.  7 


resistance.  If  .the  process  of  abrasion  be  continued  long  enough,  the 
forms,  even  of  the  large  hills,  may  be  greatly  altered,  and  their  dimen- 
sions greatly  reduced.  (Figs.  4  and  5.)  Among  the  results  of  ice 
wear,  therefore,  will  be  a  lowering  of  the  hills,  and  a  smoothing  and 
softening  of  their  contours,  while  their  surfaces  will  bear  the  marks 
of  the  tools  which  fashioned  them,  and  will  be  polished,  striated  or 
grooved,  according  to  the  nature  of  the  material  which  the  ice  pressed 
down  upon  them  during  its  passage. 


Fig.  4.    A  hill  before  the  ice  passes  over  it. 


Fig.  5.    The  same  hill  after  it  has  been  eroded  by  the  ice. 
stoss  side;  B,  the  lee  side. 


A,  the 


It  was  not  the  hills  alone  which  the  moving  ice  affected.  Where  it 
encountered  valleys  in  its  course,  they  likewise  suffered  modification. 
Where  the  course  of  a  valley  was  parallel  to  the  direction  of  the  ice 
movement,  the  ice  moved  through  it.  The  depth  of  moving  ice  is  one 
of  the  determinants  of  its  velocity,  and  because  of  the  greater  depth 
of  ice  in  valleys,  its  motion  here  was  more  rapid  than  on  the  uplands 
above,  and  its  "abrading  action  more  powerful.  Under  these  conditions 
the  valleys  were  deepened  and  widened. 

Where  the  courses  of  the  valleys  were  transverse  to  the  direction  of 
ice  movement,  the  case  was  different.  The  ice  was  too  viscous  to  span 
the  valleys,  and  therefore  filled  them.  In  this  case  it  is '  evident  that 
the  greater  depth  of  the  ice  in  the  valley  did  not  accelerate  its  motion, 
since  the  ice  in  the  valley-trough  and  that  above  it  were  in  a  measure 
opposed.    If  left  to  itself,  the  ice  in  the  valley  would  tend  to  flow  in  the 


Fig.  6.    Diagram  showing  effect  on  a  valley  of  ice  moving  traversely  across  it. 


direction  of  the  axis  of  the  valley.  Shallow  valleys  crossed  by  the  ice 
suffered  most  wear  on  the  side  opposing  ice  movements.  (Fig.  6.) 
When  deep,  narrow  valleys  were  transverse  to  the  direction  of  ice  ad- 


ATWOOD.] 


THE   GEOLOGICAL    FORMATIONS. 


13 


vance,  the  ice  that  first  entered  them  may  have  become  stationary, 
forming  a  bridge  over  which  the  main  mass  of  ice  moved.  (Fig.  7). 
In  such  cases  the  valley  did  not  suffer  much  wear. 


Pig.  7.    Diagram  to  illustrate  case  where  ice  fills  a  valley  (c)  and  the  upper 
ice  then  moves  on  over  the  filling. 

In  general,  the  effort  was  to  cut  down  prominences,  thus  tending  to 
level  the  surface.  But  when  it  encountered  valleys  parallel  to  its  move- 
ment they  were  deepened,  thus  locally  increasing  relief.  Whether  the 
reduction  of  the  hills  exceeded  the  deepening  of  the  valleys,  or  whether 
the  reverse  was  true,  so  far  as  corrasion  alone  is  concerned,  is  uncer- 
tain. But  whatever  the  effect  of  the  erosive  work  of  ice  action  upon 
the  total  amount  of  relief,  the  effect  upon  the  contours  was  to  make 
them  more  gentle.  Not  only  were  the  sharp  hills  rounded  off,  but  even 
the  valleys  which  were  deepened  were  widened  as  well,  and  in  the  pro- 
cess their  slopes  became  more  gentle.  A  river-erosion  topography, 
modified  by  the  wearing  (not  the  depositing)  action  of  the  ice,  would 
be  notably  different  from  the  original,  by  reason  of  its  gentler  slopes 
and  softer  contours.  (Figs.  4  and  5.)  The  great  lobe  of  ice  that 
moved  southward  in  the  Lake  Michigan  trough  undoubtedly  deepened 
that  depression.  The  present  bed  of  Lake  Michigan  is  at  places  about 
300  feet  below  sea  level  and  much  of  the  deepening  below  sea-level 
may  be  due  to  glacial  erosion. 

Deposition  by  the  Ice — Effect  on  Topography — On  melting,  glacier 
ice  leaves  its  bed  covered  with  the  debris  which  it  gathered  during  its 
movement.  Had  this  debris  been  equally  distributed  on  and  in  and 
beneath  the  ice  during  its  movement,  and  had  the  conditions  of  de- 
position been  everywhere  the  same,  the  drift  would  constitute  a  mantle 
of  uniform  thickness  over  the  underlying  rock.  Such  a  mantle  of  drift 
would  not  greatly  alter  the  topography;  it  would  simply  raise  the 
surface  by  an  amount  equal  to  the  thickness  of  the  drift,  leaving 
elevations  and  depressions  of  the  same  magnitude  as  before,  and  sus- 
taining the  same  relations  to  one  another.  But  the  drift  carried  by  the 
ice,  in  what  ever  position,  was  not  equally  distributed  during  trans- 
portation, and  the  conditions  under  which  it  was  deposited  were  not 
uniform,  so  that  it  produced  more  or  less  notable  changes  in  the  topo- 
graphy of  the  surface  on  which  it  was  deposited. 

The  unequal  distribution  of  the  drift  is  readily  understood.  The 
larger  part  of  the  drift  transported  by  the  ice  was  carried  in  its  basal 
portion ;  but  since  the  surface  over  which  the  ice  passed  was  variable, 
it  yielded  a  variable  amount  of  debris  to  the  ice.  Where  it  was  hilly, 
the  friction  between  it  and  the  ice  was  greater  than  where  it  was  plain, 
and  the  ice  carried  away  more  load.     From  areas  where  the  surface 


14  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

was  overspread  by  a  great  depth  of  loose  material  favorably  disposed 
for  removal,  more  debris  was  taken  than  from  areas  where  material  in 
a  condition  to  be  readily  transported  was  meager.  Because  of  the  topo- 
graphic diversity  and  lithological  heterogeneity  of  the  surface  of  the 
country  over  which  it  passed,  some  portions  of  the  ice  carried  much 
more  drift  than  others,  and  when  the  ice  finally  melted,  greater  depths 
of  drift  were  left  in  some  places  than  in  others.  Not  all  of  the  material 
transported  by  the  ice  was  carried  forward  until  the  ice  melted.  Some 
of  it  was  probably  carried  but  a  short  distance  from  its  original  posi- 
tion before  it  lodged.  Drift  was  thus  accumulating  at  some  points 
beneath  the  ice  during  its  onward  motion.  At  such  points  the  surface 
was  being  built  up ;  at  other  points,  abrasion  was  taking  place,  and  the 
surface  was  being  cut  down.  The  drift  mantle  of  any  region  does  not, 
therefore,  represent  simply  the  material  which  was  on  and  in  and 
beneath  the  ice  of  that  place  at  the  time  of  its  melting,  but  it  repre- 
sents, in  addition,  all  that  lodged  beneath  the  ice  during  its  move- 
ment. 

The  constant  tendency  was  for  the  ice  to  carry  a  considerable  part 
of  its  load  forward  toward  its  thinned  edge,  and  there  to  leave  it.  It 
follows  that  if  the  edge  of  the  ice  remained  constant  in  position  for 
any  considerable  period  of  time,,  large  quantities  of  drift  would  have 
accumulated  under  its  marginal  portion,  giving  rise  to  a  belt  of  rela- 
tively thick  drift.  Other  things  being  equal,  the  longer  the  time  dur- 
ing which  the  position  of  the  edge  was  stationary,  the  greater 
the  accumulation  of  drift.  Certain  ridge-like  belts  where  the  drift  is 
thicker  than  on  either  hand,  are  confidently  believed  to  mark  the  posi- 
tion where  the  edge  of  the  ice-sheet  stood  for  considerable  periods  of 
time. 

The  morainic  belt  of  this  type  that  is  nearest  the  region  under  con- 
sideration is  known  as  the  Valparaiso  moraine.  This  moraine  bor- 
ders Lake  Michigan  at  a  distance  of  about  20  miles  from  the  shore- 
line. It  marks  the  maximum  position  of  the  Lake  Michigan  lobe  during 
the  later  phase  of  the  Wisconsin  or  last  glacial  epoch.  West  of  Wau- 
kegan  this  moraine  crosses  the  main  line  of  the  Chicago  and  North- 
western railroad  between  the  towns  of  Cary  and  Barrington.  Farther 
south,  Glen  Elyn,  Hinsdale  and  Lemont  are  located  in  this  hilly  belt 
and  in  Indiana  the  city  of  Valparaiso,  from  which  the  moraine  received 
its  name,  is  located  within  the  belt. 

Because  of  the  unequal  amounts  of  material  carried  by  different 
parts  of  the  ice,  and  because  of  the  unequal  and  inconstant  conditions 
of  deposition  under  the  body  of  the  ice  and  its  edge,  the  mantle  of  drift 
has  a  very  variable  thickness ;  and  a  mantle  of  drift  of  variable  thick- 
ness cannot  fail  to  modify  the  topography  of  the  region  it  covers.  The 
extent  of  the  modification  will  depend  on  the  extent  of  the  variation. 
This  amounts  in  the  aggregate  to  hundreds  of  feet.  The  continental 
ice  sheet,  therefore,  modified  the  topography  of  the  region  it  covered, 
not  only  by  the  wear  it  effected,  but  also  by  the  deposits  it  made. 

In  some  places  it  chanced  that  the  greater  thicknesses  of  drift  were 
left  in  the  position  formerly  marked  by  valleys.  Locally  the  body  of 
drift  was  so  great  that  valleys  were  completely  filled,  and  therefore 
completely  obliterated  as  surface  features.     Less  frequently,  drift  not 


ATWOOD.] 


THE   GEOLOGICAL    FORMATIONS. 


15 


Fig.  8.  Diagrammatic  section  showing  relation  of  drift  to  underlying  rock,  where  the 
drift  is  thick,  relative  to  the  relief  of  the  rock.  A  and  B  represent  the  location  of  post-glacial 
valleys. 

only  filled  the  valleys  but  rose  even  higher  over  their  former  positions 
than  on  either  side.  In  other  places  the  greater  depths  of  drift,  in- 
stead of  being  deposited  in  the  valleys,  were  left  on  pre-glacial  eleva- 
tions, building  them  up  to  still  greater  heights.  In  short,  the  mantle  of 
drift  of  unequal  thickness  was  laid  down  upon  the  rock  surface  in  such 
a  manner  that  the  thicker  parts  sometimes  rest  on  hills  and  ridges, 
sometimes  on  slopes,  sometimes  on  plains,  and  sometimes  in  valleys. 
These  relations  are  suggested  by  (Fig-  8  and  9).  From  them  it  will 
be  seen  that  in  regions  where  the  thickness  of  the  drift  is  great,  rela- 
tive to  the  relief  of  the  underlying  work,  the  topography  may  be  com- 
pletely changed.  Not  only  may  some  of  the  valleys  be  obliterated  by 
being  filled,  but  some  of  the  hills  may  be  obliterated  by  having  the 
lower  land  between  them  built  up  to  their  level.  In  regions  where  the 
thickness  of  the  drift  is  slight,  relative  to  the  relief  of  the  rock  beneath, 
the  hills  cannot  be  buried,  and  the  valleys  cannot  be  completely  filled, 
so  that  the  relative  positions  of  the  principal  topographic  features  will 
remain  much  the  same  after  the  deposition  of  the  drift,  as  before 
(Fig.  B). 


Fig.  9.      Diagrammatic  section  showing  relation  of  drift  to  underlying  rock  where  the  drift 
is  thin  relative  to  the  relief  of  the  underlying  rock. 


In  case  the  pre-glacial  valleys  were  filled  and  the  hills  buried,  the 
new  valleys  which  the  surface  waters  will  in  time  cut  in  the  drift  sur- 
face will  have  but  little  correspondence  in  position  with  those  which 
existed  before  the  ice  incursion.  A  new  system  of  valleys,  and  there- 
fore a  new  system  of  ridges  and  hills,  will  be  developed,  in  some  meas- 
ure independent  of  the  old.    These  relations  are  illustrated  by  Fig.  8 

Inequalities  in  the  thickness  of  drift  lead  to  a  still  further  modifica- 
tion of  the  surface.  It  frequently  happened  that  in  a  plane  or  nearly 
plane  region,  a  slight  thickness  of  drift  was  deposited  at  one  point, 
while  all  about  it  much  greater  thicknesses  were  left.  The  area  of  thin 
drift  would  then  constitute  a  depression,  surrounded  by  a  higher  sur- 
face built  up  by  the  thicker  deposits.  Such  depressions  would  at  first 
have  no  outlets,  and  are  therefore  unlike  the  depressions  shaped  by  rain 
and  river  erosion.     The  presence  of  depressions  without  outlets  is  one 


16  THE    EVANSTON- WAUKEGAN    REGION.  Ibull.  7 

of  the  marks  of  a  drift-covered  (glaciated)  country.  In  these  depres- 
sions water  may  collect,  forming  lakes  or  ponds,  or  in  some  cases  only 
marshes  and  bogs. 

The  thickness  of  drift  in  the  Evanston-Waukegan  region  is  so  great 
that  the  underlying  rock  topography  is  obliterated,  and  the  rolling  sur- 
face of  the  upland  is  due  entirely  to  the  distribution  of  the  drift.  There 
are  numerous  undrained  depressions  in  the  upland  surface,  and  many 
of  them  contain  ponds  or  marshes,  especially  during  the  spring. 

In  the  farming  district  about  Waukegan  there  are  numerous  wells 
75  to  ioo  feet  deep  in  which  bed-rock  was  not  reached.  Southwest  of 
Lake  Forest,  on  L.  F.  Swift's  farm,  there  is  a  well  280  feet  deep  in  drift 
and  one  mile  farther  west  another  well  down  180  feet,  without  strik- 
ing bed-rock. 

In  the  following  cases  rock  was  reached,  and  therefore  the  thickness 
of  drift  determined: 

1.  At  Mrs.  M.  J.  Durkin's,  three  miles  north  of  Waukegan,  bed-rock  was 
reached  at  150  feet.    The  well  is  175  feet  deep. 

2.  At  H.  W.  Ferry's,  four  and  one-half  miles  north  of  Waukegan,  bed-rock 
was  reached  at  128  feet. 

3.  Three  miles  west  of  Waukegan  on  a  farm  owned  by  Mrs.  Durkin,  bed- 
rock was  reached  at  90  feet. 

4.  At  L.  P.  Swift's  artesian  well,  Lake  Forest,  bed-rock  was  reached  at 
212  feet.     The  well  is  989  feet  deep. 

5.  At  Mr.  Booth's  well,  a  quarter  of  a  mile  southwest  of  Mr.  Swift's, 
bed-rock  was  reached  at  about  280  feet. 

6.  At  C.  B.  Farwell's  artesian  well,  Lake  Forest,  rock  was  struck  at  160 
feet* 

7.  In  Highland  Park  rock  was  struck  at  160  to  175  feet.f 

8.  At  Mr.  Lloyds'  artesian  well,  in  the  north  part  of  Winnetka,  rock  was 
struck  at  150  feet* 

9.  In  Ravina  a  well  reaches  bed-rock  at  164  feet* 

10.  At  Dr.  Oliver  Marcy's,  South  Evanston,  bed-rock  was  found  72  feet 
below  the  surface.f 

The  average  thickness  of  drift  in  the  upland  region  is  probably  about  150 
feet,  and  in  the  lake  plain  areas  from  50  to  75  feet.  In  most  places  the  sur- 
face of  the  rock  is  well  below  the  surface  of  the  lake. 

Direction  of  Ice  Movement — The  direction  in  which  glacier  ice 
moved  may  be  determined  in  various  ways,  even  after  the  ice  has  dis- 
appeared. The  shapes  of  the  rock  hills  over  which  the  ice  passed 
(p.  12),  the  direction  from  which  the  materials  of  the  drift  came, 
the  striations  on  bed-rock,  and  the  course  of  the  margin  of  the  drift, 
are  all  used  in  making  such  determinations.  From  the  course  of  the 
drift  margin,  the  general  direction  of  movement  may  be  inferred  when 
it  is  remembered  that  the  tendency  of  glacier  ice  on  a  plane  surface  is 
to  move  at  right  angles  to  its  margin. 

For  the  exact  determination  of  the  direction  of  ice  movement,  re- 
course must  be  had  to  the  striae  on  the  bed-rock.  Were  the  striated 
rock  surface  perfectly  plane,  and  were  the  striae  even  lines,  they  would 
only  tell  that  the  ice  was  moving  in  one  of  two  directions.  But  the 
rock  surface  is  not  usually  perfectly  plane,  nor  the  striae  even  lines, 


*  From  the  Pleistocene  Features  and  Deposits  of  the  Chicago  Area;  Frank  Leverett.  Bull, 
2,  Geol.  and  Nat.  Hist.  Surv.,  Chicago  Acad,  of  Sci. 

t  Frank  Leverett.  in  17th  Ann.  Rept.  U.  S.  Geol.  Surv.,  Pt.  II,  P.  800. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PL  1. 


WW 


Fig.  A. 


Glaciated  stones  showing  both  form  and  striae 
LCourtesy  of  Wisconsin  Geo).  Nat.  Hist.  Surv.] 


(Matz.) 


Fig.  B.    Limestone  bowlder  in  north  fork  of 
Pettibone  Creek,  North  Chicago. 


Fig.  C.      Igneous  bowlder  at  Northwestern 
Railway  station,  Waukegan. 


atwood.]  THE   GEOLOGICAL    FORMATIONS.  17 

and  between  the  two  directions  which  lines  alone  might  suggest,  it  is 
usually  possible  to  decide.  The  minor  prominences  and  depressions  in 
the  rock  surface  were  shaped  according  to  the  same  principles  that 
govern  the  shaping  of  hills  (Fig.  5)  and  valleys  (Fig.  6)  ;  that  is,  the 
proximal  or  stoss  (struck)  sides  of  the  minor  prominences,  and  the 
distal  sides  of  small  depressions  suffered  tie  more  wear.  With  a  good 
compass,  the  direction  of  the  striae  may  be  measured  to  within  a  frac- 
tion of  a  degree,  and  thus  the  direction  of  ice  movement  in  a  particu- 
lar place  be  definitely  determined. 

In  the  Evanston-Waukegan  area  the  source  of  the  material  in  the 
drift  is  the  only  guide  in  determining  the  direction  from  which  the  ice 
came,  but  from  the  study  of  a  larger  area  it  is  known  that  the  ice  which 
invaded  this  region  moved  southward  through  the  Lake  Michigan 
trough,  spreading  westward  over  the  bordering  lands  on  the  west  side 
of  the  lake. 

Effect  of  Topography  on  Movement — The  effect  of  glaciation  on  to- 
pography has  been  outlined,  but  the  topography  in  turn  exerted  an  im- 
portant influence  on  the  direction  of  ice  movement.  The  extreme  de- 
gree of  topographic  influence  is  seen  in  mountain  regions  like  the  Alps, 
where  most  of  the  glaciers  are  confined  strictly  to  the  valleys. 

As  an  ice  sheet  invades  a  region,  it  advances  first  and  farthest  along 
the  lines  of  least  resistance.  In  a  rough  country  with  great  relief, 
tongues  or  lobes  of  ice  push  forward  in  the  valleys,  while  the  hills  or 
other  prominences  tend  to  hold  back  or  divide  the  onward  moving 
mass.  The  edge  of  an  ice  sheet  in  such  a  region  would  be  irregular. 
The  marginal  lobes  of  ice  occupying  the  valleys  would  be  separated 
by  re-entrant  angles  marking  the  sites  of  hills  and  ridges. 

As  the  ice  advanced  southwestward  from  the  Laborador  center  of 
accumulation  (Fig.  3)  one  lobe  followed  the  Lake  Superior  trough 
and  another  lobe  moved  through  the  Lake  Michigan  trough.  There 
was,  therefore,  relatively  less  ice  to  move  directly  southwestward  over 
the  Wisconsin  region.  These  conditions  help  to  account  for  the  drift- 
less  or  unglaciated  region  in  the  southwestern  portion  of  Wisconsin. 
The  Green  Bay  lobe  (Fig.  30)  developed  on  the  west  flank  of  the  Lake 
Michigan  lobe,  and  was  led  off  by  the  depression  in  that  direction. 

GLACIAL   DEPOSITS. 

General  Characteristics — When  the  ice  of  the  continental  glacier  be- 
gan its  motion,  it  carried  none  of  the  stony  and  earthy  debris  which 
constitutes  the  drift.  These  materials  were  derived  from  the  surface 
over  which  the  ice  moved. 

From  the  method  by  which  it  was  gathered,  it  is  evident  that  the 
drift  of  any  locality  may  contain  fragments  of  rock  of  every  variety 
which  occurs  along  the  route  followed  by  the  ice  which  reached  that 
locality.  When  the  ice  had  moved  far,  and  when  there  were  frequent 
changes  in  the  character  of  the  rock  constituting  its  bed,  the  variety  of 
materials  in  the  drift  is  great.  The  heterogeneity  of  the  drift  arising 
from  the  diverse  nature  of  the  rocks  which  contributed  to  it  is  litho- 

—2  G. 


18  THE    EVANSTON-WAUKEGAN    REGION.  I  bull.  7 

logical  heterogeneity — a  term  which  implies  the  commingling  of  mater- 
ials derived  from  different  rock  formations.  Thus  it  is  common  to  find 
pieces  of  sandstone,  limestone,  quartzite,  granite,  gneiss,  schist,  etc., 
intimately  commingled  in  the  drift,  wherever  the  ice  which  produced 
it  passed  over  formations  of  these  several  sorts  of  rock.  Lithological 
heterogeneity  is  one  of  the  notable  characteristics  of  glacial  formations. 
In  the  Evanston-Waukegan  region  the  glacial  sands  commonly  con- 
tain particles  of  quartz,  feldspar,  hornblende,  augite,  pyrite,  and  mag- 
netite. When  the  sand  is  dry,  the  magnetite  may  be  easily  withdrawn 
from  the  other  grains  by  a  magnet.  The  pebbles  and  large  stones  of 
the  drift  include  the  following: 

1.  Red  sandstone,  compact  and  fine  grained. 

2.  Yellow  sandstone,  coarse  grained  and  friable. 

3.  Mottled  sandstone,  red  and  yellow. 

4.  Brown  sandstone,  rich  in  iron  oxides. 

5.  Red  quartzite,  compact  and  hard  but  with  sand  grains  noticeable. 

6.  Conglomerate,  composed  of  sand  and  gravel  and  due  to  local  cementa- 
tion. 

7.  White  limestone,  compact  and  hard. 

8.  Possiliferous  limestone,  composed  largely  of  shells. 

9.  Marble,  finely  crystalline. 

10.  Shale,  soft,  with  layers  that  part  easily. 

11.  Slate,  hard,  with  layers  that  part  easily. 

12.  Red  granite,  pink  and  red  feldspar  crystals  predominating. 

13.  Gray  granite,  white  feldspar  crystals  predominating. 

14.  Syenite,  like  granites  but  with  little  or  no  quartz. 

15.  Diorite,  quartz  and  feldspar  present  but  black  hornblende  crystals 
predominating. 

16.  Gabbro,  quartz  and  feldspar  present  but  black  pyroxene  crystals  pre- 
dominating. 

17.  Porphyry,  quartz  phenocrysts  most  common. 

18.  Basalt,  dark  green  or  black  and  very  finely  crystalline. 

19.  Gneiss,  banded. 

20.  Schist,  more  closely  banded  than  gneiss,  and  often  appears  to  be  in 
layers. 

21.  Quartz,  white,  glassy  and  very  hard. 

22.  Jaspar,  red,  fine  textured  and  very  hard. 

23.  Flint,  gray  or  black,  brittle,  glassy  and  very  hard. 

24.  Chert,  white,  brittle,  and  very  hard. 

25.  Pyrite,  light  yellow  and  heavy. 

Collections  of  these  sorts  of  rock  may  easily  be  made  almost  any- 
where on  the  beach,  but  stony  material  is  most  accessible  near  North 
Chicago,  and  southward  to  Lake  Bluff,  and  near  Glencoe  and  Lake- 
side. 

Another  characteristic  of  the  drift  is  its  physical  heterogeneity.  As 
first  gathered  from  the  bed  of  moving  ice,  some  of  the  material  of  the 
drift  was  fine  and  some  coarse.  The  tendency  of  the  ice  in  all  cases 
was  to  reduce  its  load  to  a  still  finer  condition.  Some  of  the  softer 
materials,  such  as  soft  shale,  were  crushed  or  ground  to  powder, 
forming  what  is  commonly  known  as  clay.  Clayey  (fine)  material  is 
likewise  produced  by  the  grinding  action  of  ice-carried  bowlders  upon 
the  rock-bed,  and  upon  one  another.  Other  sorts  of  rock,  such  as  soft 
sandstone,  were  reduced  to  the  physical  condition  of  sand,  instead  of 
clay,  and  from  sand  to  bowlders  all  grades  of  coarseness  and  fineness 
are  represented  in  the  glacial  drift. 


atwood.]  THE   GEOLOGICAL    FORMATIONS.  19 

The  two  largest  bowlders  known  to  the  writer,  in  this  region,  are: 

1.  A  gray  magnesian  limestone  fully  8  feet  in  length  and  located  on  the 
beach  near  Glencoe.  This  bowlder  is  near  the  base  of  the  cliff  and  a  few 
rods  north  of  the  east-west  road  nearest  the  Northwestern  railroad  station. 
The  upper  surface  is  beautifully  striated. 

2.  A  gray  magnesian  limestone  bowlder  in  the  North  Branch  of  Petti- 
bone  creek.  This  rock  is  15  feet  in  length  and  may  be  found  by  following 
the  creek  down  stream  from  North  Chicago.  It  is  on  the  left  side  and  about 
20  feet  above  the  water  (Fig.  B,  Plate  I).  The  surfaces  of  this  bowlder  are 
also  striated. 

The  limestone  bowlders  are  of  relatively  local  origin  and  may 
have  been  carried  but  a  few  miles.  The  igneous  rock  at  Waukegan 
has  come  at  least  300  miles,  and  may  have  come  much  farther. 

Since  the  ice  does  not  assort  the  material  which  it  carries,  as  water 
does,  the  clay,  sand,  gravel  and  bowlders  will  not,  by  the  action  of  the 
ice,  be  separated  from  one  another.  .  They  are  therefore  not  stratified. 
As  left  by  the  ice,  these  phyically  heterogeneous  materials  are  confus- 
sedly  commingled.  The  finer  parts  constitute  a  matrix  in  which  the 
coarser  are  embedded. 

Physical  heterogeneity  (Plate  II),  therefore,  is  another  characteristic 
of  glacial  drift.  It  is  not  to  be  understood  that  the  proportions  of  these 
various  physical  elements,  clay,  sand,  gravel  and  bowlders,  are  con- 
stant. Locally  any  one  of  them  may  predominate  over  any  or  all  the 
others  to  any  extent. 

Since  Hthological  and  physical  heterogeneity  are  characteristics  of 
glacial  drift,  they  together  afford  a  criterion  which  is  often  of  service 
in  distinguishing  glacial  drift  from  other  surface  formations.  It  fol- 
lows that  this  double  heterogeneity  constitutes  a  feature  which  can  be 
utilized  in  determining  the  former  extension  of  existing  glaciers,  as 
well  as  the  former  existence  of  glaciers  where  glaciers  do  not  now 
exist. 

Another  characteristic  of  glacial  drift,  and  one  which  clearly  dis- 
tinguishes it  from  all  other  formations  with  which  it  might  be  con- 
founded, is  easily  understood  from  its  method  of  formation.  If  the 
ice  in  its  motion  holds  down  rock  debris  upon  the  rock  surface  over 
which  it  passes  with  such  pressure  as  to  polish  and  striate  the  bed-rock, 
the  material  carried  will  itself  suffer  wear  comparable  to  that  which 
it  inflicts.  Thus  the  stones,  large  and  small,  of  glacial  drift,  will  be 
smoothed  and  striated.  This  sort  of  wear  on  the  transported  blocks 
of  rock,  is  effected  both  by  the  bed-rock  reacting  on  the  bowlders 
transported  over  it.  and  by  bowlders  acting  on  one  another  in  and  un- 
der the  ice.  The  wear  of  bowlders  by  bowlders  is  effected  wherever 
adjacent  ones  are  carried  along  at  different  rates.  Since  the  rate  of 
motion  of  the  ice  is  different  in  different  parts  of  the  glacier,  the  mu- 
tual abrasion  of  transported  materials  is  a  process  constantly  in  opera- 
tion. A  large  proportion  of  the  transported  stone  and  blocks  of  rock 
may  thus  eventually  become  striated. 

From  the  nature  of  the  wear  to  which  the  stones  are  subjected  when 
carried  in  the  base  of  the  ice,  it  is  easy  to  understand  that  their  shapes 
must  be  different  from  those  of  water-worn  materials.  The  latter  are 
rolled  over  and  over,  and  thus  lose  all  their  angles  and  assume  a  more 


20  THE    EVANSTON-WAUKEGAN    REGION.  [bull.  7 

or  less  rounded  form.  The  former,  held  more  or  less  firmly  in  the  ice, 
and  pressed  against  the  underlying  rock  or  rock  debris  as  they  are 
carried  slowly  forward,  have  their  faces  planed  and  striated.  The  plan- 
ation  and  striation  of  a  stone  need  not  be  confined  to  its  under  surface. 
On  either  side  or  above  it  other  stones,  moving  at  different  rates,  are 
made  to  abrade  it,  so  that  its  top  and  sides  may  be  planed  and  scored. 
If  the  ice-carried  stones  shift  their  positions,  as  they  may  under  var- 
ious circumstances,  new  faces  will  be  worn.  The  new  face  thus 
planed  off  may  meet  those  developed  at  an  earlier  time  at  sharp  angles, 
altogether  unlike  anything  which  water-wear  is  capable  of  producing. 
The  stone  thus  acted  upon  shows  a  surface  bounded  by  planes  and 
more  or  less  beveled,  instead  of  a  rounded  surface  such  as  water-wear 
produces.  We  find,  then,  in  the  shape  of  the  bowlders  and  smaller 
stones  of  the  drift,  and  in  the  markings  upon  their  surfaces,  additional 
criteria  for  the  identification  of  glacier  drift  (Plate  I,  Fig.  A). 

The  characteristics  of  glacial  drift,  so  far  as  concerns  its  constitution, 
may  then  be  enumerated  as,  (i)  its  lithological,  and  (2)  physical  heter- 
ogeneity, (3)  the  shapes,  and  (4)  the  markings  of  the  stones  of  the 
drift.     In  structure,  the  drift  which  is  strictly  glacial,  is  unstratified. 

In  the  broadest  sense  of  the  term,  all  deposits  made  by  glacier  ice 
are  moraines.  Those  made  beneath  the  ice  and  back  from  its  edge 
constitute  the  ground  moraine,  and  are  distinguished  from  the  consid- 
erable marginal  accumulations  which,  under  certain  conditions,  are  ac- 
cumulated at  or  near  the  margin.  These  marginal  accumulations  are 
terminal  moraines.  Associated  with  the  moraines  which  are  the  de- 
posits of  the  ice  directly,  there  are  considerable  bodies  of  stratified 
gravel  and  sand,  the  structure  of  which  shows  that  they  were  laid  down 
by  water.  This  is  to  be  especially  noted,  since  lack  of  stratification  is 
popularly  supposed  to  be  the  especial  mark  of  the  formations  to  which 
the  ice  gave  rise. 

These  deposits  of  stratified  drift  lie  partly  beyond  the  terminal  mor- 
aine, and  partly  within  it.  They  often  sustain  very  complicated  rela- 
tions both  in  the  ground  and  terminal  moraines.  The  drift  as  a  whole 
is  therefore  partly  stratified  and  partly  unstratified.  Structurally  the 
two  types  and  thoroughly  distinct,  but  their  relations  are  often  most 
complex,  both  horizontally  and  vertically. 

GROUND   MORAINE. 

Distribution — The  ground  moraine  constitutes  the  great  body  of  the 
glacial  drift.  Bowlder  clay,  a  term  descriptive  of  its  constitution  in 
some  places,  and  till,  are  other  terms  often  applied  to  the  ground  mor- 
aine. The  ground  moraine  consists  of  all  the  drift  which  lodged 
beneath  the  ice  during  its  advance,  all  that  was  deposited  back  from  its 
edge  while  its  margin  was  farthest  south,  and  most  of  that  which  was 
deposited  while  the  ice  was  retreating.  From  this  mode  of  origin  it  is 
readily  seen  that  the  ground  moraine  should  be  essentially  as  wide- 
spread as  the  ice  itself.  Locally,  however,  it  failed  of  deposition.  Since 
it  constitutes  the  larger  part  of  the  drift,  the  characteristics  already 


atwood.]  THE   GEOLOGICAL    FORMATIONS.  21 

enumerated  as  belonging  to  drift  in  general  are  the  character- 
istics of  the  till.  Wherever  obstacles  to  the  progress  of  the  ice  lay 
in  its  path,  there  was  a  chance  that  these  obstacles,  rising  somewhat 
into  the  lower  part  of  the  ice,  would  constitute  barriers  against  which 
debris  in  the  lower  part  of  the  ice  would  lodge.  It  might  happen  also 
that  the  ice,  under  a  given  set  of  conditions  favoring  erosion,  would 
gather  a  greater  load  of  rock-debris  than  could  be  transported  under 
the  changed  conditions  into  which  its  advance  brought  it.  In  this  case, 
some  part  of  the  load  would  be  dropped  and  over-ridden.  Especially 
near  the  margin  of  the  ice  where  its  thickness  was  slight  and  diminish- 
ing, the  ice  must  have  found  itself  unable  to  carry  forward  the  loads 
of  debris  which  it  had  gathered  farther  back  where  its  action  was  more 
vigorous.  It  will  be  readily  seen  that  if  not  earlier  deposited,  all  mater- 
ial gathered  by  the  under  surface  of  the  ice  would  ultimately  find  itself 
at  the  edge  of  the  glacier,  for  given  time  enough,  ablation  will  waste 
all  that  part  of  the  ice  occupying  the  space  between  the  original  posi- 
tion of  the  debris,  and  the  margin  of  the  ice.  Under  the  thinned  margin 
of  the  ice,  however,  considerable  accumulations  of  drift  must  have  been 
taking  place  while  the  ice  was  advancing.  While  the  edge  of  the  ice 
sheet  was  advancing  into  territory  before  uninvaded,  the  material  ac- 
cumulated beneath  its  edge  at  one  time,  found  itself  much  farther  from 
the  margin  at  another  and  later  time.  Under  the  more  forcible  ice 
action  back  from  the  margin,  the  earlier  accumulations,  made  under  the 
thin  edge,  were  partially  or  wholly  removed  by  the  thicker  ice  of  a 
later  time,  and  carried  down  to  or  toward  the  new  and  more  advanced 
margin.  Here  they  were  deposited,  to  be  in  turn  distributed  and  trans- 
ported still  farther  by  the  farther  advance  of  the  ice. 

Since  in  its  final  retreat  the  margin  of  the  ice  must  have  stood  at 
all  points  once  covered  by  it,  these  submarginal  accumulations  of  drift 
must  have  been  made  over  the  whole  country  once  covered  by  the  ice. 
The  deposits  of  drift  made  beneath  the  marginal  part  of  the  ice  during 
its  retreat,  would  either  cover  the  deposits  made  under  the  body  of  the 
ice  at  an  earlier  time,  or  be  left  alongside  them.  The  constitution  of 
the  two  phases  of  till,  that  deposited  during  the  advance  of  the  ice, 
and  that  deposited  during  its  retreat,  is  essentia11'  the  same,  and  there 
is  nothing  in  their  relative  positions,  to  sharply  differentiate  them. 
They  are  classed  together  as  subglacial  till. 

Subglacial  till  was  under  the  pressure  of  the  overlying  ice.  In  keep- 
ing with  these  conditions  of  accumulation,  the  till  often  possesses  a 
firmness  suggestive  of  great  compression.  Where  its  constitution  is 
clayey  it  is  often  remarkably  tough.  Wrhere  this  is  the  case,  the  qual- 
ity here  referred  to  has  given  rise  to  the  suggestive  name  "hard  pan." 
Where  the  constitution  of  the  till  is  sandy,  rather  than  clayey,  this  firm- 
ness and  toughness  are  less  developed,  or  may  be  altogether  wanting, 
since  sand  cannot  be  compressed  into  coherent  masses  like  clay. 

Constitution — The  till  is  composed  of  the  more  or  less  comminuted 
materials  derived  from  the  land  across  which  the  ice  passed.  The  foil 
and  all  the  loose  materials  which  covered  the  rock  entered  into  its 
composition.     Where  the  ice  was  thick  and  its  action  vigorous,  it  not 


22  THE   EVANSTON-WAUKEGAN    REGION.  [bulk  7 

only  carried  away  the  loose  material  which  it  found  in  its  path,  but, 
armed  with  this  material,  it  abraded  the  underlying  rock,  wearing  down 
its  surface  and  detaching  large  and  small  blocks  of  rock  from  it.  It 
follows  that  the  constitution  of  the  till  at  any  noint  is  dependent  upon 
the  nature  of  the  soil  and  rock  from  which  it  was  derived. 

If  sandstone  be  the  formation  which  has  contributed  most  largely  to 
the  till,  the  matrix  of  the  till  will  be  sandy.  Where  limestone  instead 
of  sandstone  made  the  leading  contribution  to  it,  the  till  has  a  more 
earthy  or  clayey  matrix.  Any  sort  of  rock  which  may  be  very  generally 
reduced  to  a  fine  state  of  division  under  the  mechanical  action  of  the 
ice,  will  give  rise  to  clayey  till. 

The  nature  and  the  number  of  the  bowlders  in  the  till,  no  less  than 
the  finer  parts,  depend  on  the  character  of  the  rock  overridden.  A  hard 
and  resistant  rock,  such  as  quartzite,  will  give  rise  to  more  bowlders 
in  proportion  to  the  total  amount  of  material  furnished  to  the  ice,  than 
will  softer  rock.  Shale  or  soft  sandstone,  possessing  relatively  slight 
resistance,  will  be  much  more  completely  crushed.  They  will,  there- 
fore, yield  proportionately  fewer  bowlders  than  harder  formations,  and 
more  of  the  finer  constituents  of  till. 

The  bowlders  taken  up  by  the  ice  as  it  advanced  over  one  sort  of  rock 
and  another,  possessed  different  degrees  of  resistance.  The  softer  ones 
were  worn  to  smaller  dimensions  or  crushed  with  relative  ease  and 
speed.  Bowlders  of  soft  rock,  are  therefore,  not  commonly  found  in 
any  abundance  at  great  distances  from  their  sources.  The  harder  ones 
yielded  less  readily  to  abrasion,  and  were  carried  much  farther  before 
being  destroyed,  though  even  such  must  have  suffered  constant  re- 
duction in  size  during  their  subglacial  journey.  In  general  it  is  true 
that  boulders  in  the  till,  near  their  parent  formations,  are  larger  and 
less  worn  than  those  which  have  been  transported  great  distances. 

The  ice  which  covered  this  region  had  come  a  great  distance  and  had 
passed  over  rock  formations  of  many  kinds.  The  till  therefore  con- 
tains elements  derived  from  various  formations ;  that  is,  it  is  litho- 
logically  heterogeneous.  This  heterogeneity  can  not  fail  to  attract 
the  attention  of  one  examining  any  of  the  many  exposures  of  drift 
along  the  lake  shore  or  the  stones  lodged  on  the  beach. 

In  general  the  till  of  any  locality  is  made  up  largely  of  material  de- 
rived from  the  formations  close  at  hand.  This  fact  seems  to  afford 
sufficient  warrant  for  the  conclusion  that  a  considerable  amount  of 
deposition  must  have  gone  on  beneath  the  ice  during  its  movement, 
even  back  from  its  margin.  To  take  a  concrete  illustration,  it  would 
seem  that  the  drift  of  the  Evanston-Waukegan  region  should  have  had 
a  larger  contribution  than  it  has  of  material  derived  from  Canadian 
territory,  if  material  once  taken  up  by  the  ice  was  all  or  chiefly  carried 
down  to  its  thinned  edge  before  deposition.  The  fact  that  so  little  of 
the  drift  came  from  these  distant  sources  would  seem  to  prove  that  a 
large  part  of  the  material  moved  by  the  ice,  is  moved  a  relatively  short 
distance  only.  The  ice  must  be  conceived  of  as  continually  depositing 
parts  of  its  load,  and  parts  which  it  has  carried  but  a  short  distance,  as 
it  takes  up  new  material  from  the  territory  newly  invaded.  In  keep- 
ing with  the  character  of  till  in  general,  that  of  this  region  was  de- 
rived largely  from  limestone. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PL  2. 


Pig.  A.     Abandoned  clay  pit  near  Fort  Sheridan.      [Courtesy  of  the  C.  &  N.  W.  Ry, 


Fig.  B.    Sketch  of  ground  moraine  topography. 


Fig.  C.    Sketch  of  terminal  moraine  topography. 


ATWOOD.]  THE    GEOLOGICAL    FORMATIONS.  23 

Topography — The  topography  of  the  ground  moraine  is  in  general 
the  topography  already  described  (pp.  13-15)  in  considering  the  modi- 
fication of  preglacial  topography  effected  by  ice  deposition.  As  left  by 
the  ice,  its  surface  was  undulating.  (Plate  II,  Fig.  B.)  The  undula- 
tions did  not  take  the  form  of  hills  and  ridges  with  intervening  valleys, 
but  of  swells  and  depressions  standing  in  no  orderly  relationship  to 
one  another.  Undrained  depressions  are  found  in  the  ground  moraine, 
but  they  are,  as  a  rule,  broader  and  shallower  than  the  "kettles"  com- 
mon to  terminal  moraines  (Plate  II,  Fig.  C.)  It  is  in  the  broad,  shallow 
depressions  that  many  of  the  lakes  and  more  of  the  marshes  of  south- 
eastern Wisconsin  are  located. 

The  rolling,  undulating  topography  characteristic  of  ground  mo- 
raines is  well  shown  just  west  of  the  Chicago  and  Northwestern  road 
between  Glencoe  and  Waukegan.  North  of  Waukegan,  the  upland 
is  typical  ground  moraine,  but  the  lowland  is  an  ancient  lake  flat. 

When  the  entire  morainic  area  from  the  shore  of  Lake  Michigan  to 
the  Des  Plaines  river  is  considered,  it  is  found  to  consist  of  three 
somewhat  distinct  north-south  ridges*  separated  by  lowlands  of  gently 
rolling  topography.  The  west  ridge  decreases  in  height  to  the  south, 
and  dies  out  in  a  plain  near  Mont  Clare  in  the  southwestern  part  of 
Jefferson  township.  The  southern  terminus  of  the  middle  ridge  is  near 
the  head  of  the  Chicago  river,  and  at  the  border  of  the  former  extension 
of  the  lake.  The  eastern  ridge  is  the  one  with  which  we  are  chiefly 
concerned  in  the  north  shore  region.  This  ridge  extends  from  the 
northern  boundary  of  the  State  southward  to  Winnetka,  where  it  is 
intersected  by  the  present  lake  shore.  The  most  easterly  of  these 
ridges  rises  about  100  feet  above  the  lake,  a  mile  back  from  the  shore. 
Its  crest  is  followed  by  the  C.  &  N.  W.  railway  for  some  miles.  These 
ridges  still  remain  much  as  the  ice  left  them.  The  time  which  has 
elapsed  since  the  ice  disappeared  from  the  region  has  been  too  short 
for  them  to  have  been  greatly  changed.  A  bowlder  train  on  the  lake 
bottom  was  reported  by  Lyman  Cooley,  of  the  Chicago  Drainage 
Commission  as  running  southeastward  for  several  miles  from  the  ter- 
minus of  this  ridge,  and  Mr.  Leverett  thinks  this  may  be  the  residue 
from  the  till  ridge  which  has  been  cut  away  by  the  lake.+  Aside  from 
the  ravines  the  upland  of  the  Evanston-Waukegan  region  has  a  ground 
moraine  topography.  If  the  ravines  were  filled  and  the  rolling  upland 
extended  eastward,  descending  gradually  to  the  lake  level,  the  surface 
as  left  by  the  ice  would  be  essentially  reproduced. 

TERMINAL  MORAINES. 

Formation — The  marginal  portion  of  the  ice  sheet  was  more  heavily 
loaded — certainly  more  heavily  loaded  relative  to  its  thickness — than 
any  other.  Toward  its  margin,  the  thinned  ice  was  constantly  losing 
its  transportive  poWer,  and  at  its  edge  this  power  was  altogether  gone. 
Since  the  ice  was  continually  bringing  drift  down  to  this  position  and 


*  These  ridges  have  been  fully  described  by  Leverett  in  "The  Pleistocene  Features  and 
Deposits  of  the  Chicago  Area."  Bull.  2,  p.  42,  Geol.  and  Nat.  Hist.  Surv.,  Chicago  Acad,  of 
Sci. 

t  For  fuller  discussion  see  Chicago  Folio  U.  S.  Geol.  Surv.,  p.  6,  by  Wm.  C  Alden. 


24  THE    EYANSTON-WAUKEGAN    REGION.  [bull.  7 

leaving  it  there,  the  rate  of  drift  accumulation  must  have  been  greater, 
on  the  average,  beneath  the  edge  of  the  ice  than  elsewhere. 

Whenever,  at  any  stage  of  its  history,  the  edge  of  the  ice  remained 
essentially  constant  in  position  for  a  long  period,  the  corresponding 
submarginal  accumulation  of  drift  was  great,  and  when  the  ice  melted, 
the  former  site  of  the  stationary  edge  would  be  marked  by  a  broad 
ridge  or  belt  of  drift,  thicker  than  that  on  either  side.  Such  thickened 
belts  or  drift  are  terminal  moraines.  It  will  be  seen  that  a  terminal  mo- 
raine does  not  necessarily  mark  the  terminus  of  the  ice  at  the  time  of 
its  greatest  advance,  but  rather  its  terminus  at  any  time  when  its  edge 
was  stationary  or  nearly  so. 

These  submarginal  moraines  are  often  made  of  materials  identical 
with  those  which  constitute  the  ground  moraine.  Such  materials  as 
were  carried  on  the  ice  were  dropped  at  its  edge  when  the  ice  which 
bore  them  melted  from  beneath.  If  the  surface  of  the  ice  carried 
many  bowlders,  many  would  be  dropped  along  the  line  of  its  edge 
wherever  it  remained  stationary  for  any  considerable  period  of  time. 
A  terminal  moraine,  therefore,  embraces  (i)  the  thick  belt  of  drift 
accumulated  beneath  the  edge  of  the  ice  while  it  was  stationary,  or 
nearly  so;  and  (2)  such  debris  as  was  carried  on  the  surface  of  the 
ice  and  dumped  at  its  margin.  In  general  the  latter  is  relatively 
unimportant. 

Topography  of  terminal  moraines — The  most  distinctive  feature  of 
a  terminal  moraine  is  not  its  ridge-like  character,  but  its  peculiar 
topography.  In  general,  it  is  marked  by  depressions  without  outlets, 
associated  with  hillocks  and  short  ridges  comparable  in  dimensions 
to  the  depressions  (Plate  II,  Fig.  C).  Both  elevations  and  depres- 
sions are,  as  a  rule,  more  abrupt  than  in  the  ground  moraine.  In  the 
depressions  there  are  many  marshes,  bogs,  ponds  and  small  lakes. 
The  shapes  and  the  abundance  of  round  and  roundish  hills  have  locally 
given  rise  to  such  names  as  "The  Knobs,"  "Short  Hills,"  etc.  Else- 
where the  moraine  has  been  named  the  "Kettle  Range,"  from  the 
number  of  kettle-like  depressions  in  its  surface.  It  is  to  be  kept  in 
mind  that  it  is  the  association  of  the  "knobs"  and  "kettles,"  rather 
than  either  feature  alone,  which  is  the  distinctive  mark  of  terminal 
moraine  topography.  Terminal  moraines  have  no  distinct  develop- 
ment within  the  area  here  described,  and  are  mentioned  here  only 
for  general  contrast  with  the  ground  moraine. 

STRATIFIED   DRIFT. 

While  it  is  true  that  glacier  ice  does  not  distinctly  stratify  the  de- 
posits which  it  makes,  it  is  still  true  that  a  very  large  part  of  the  drift 
for  which  the  ice  of  the  glacial  period  was  directly  or  indirectly  re- 
sponsible is  stratified.  That  this  should  be  so  is  not  strange  when  it  is 
remembered  that  most  of  the  ice  was  ultimately  converted  into  running 
water,  just  as  the  glaciers  of  today  are.  The  relatively  small  portion 
which  disappeared  by  evaporation  was  probably  more  than  counter- 
blanced,  at  least  near  the  margin  of  the  ice,  by  the  rain  which  fell 
upon  it.     It  can  not  be  considered  an  exaggeration,  therefore,  to  say 


THE  GEOLOGICAL  FORMATIONS. 


25 


that  the  total  amount  of  water  which  operated  on  the  drift,  first  and 
last,  was  hardly  less  than  the  total  amount  of  the  ice  itself.  The  drift 
deposited  by  the  marginal  part  of  the  ice  was  affected  during  its  depo- 
sition, not  only  by  the  water  which  arose  from  the  melting  of  the  ice 
which  did  the  depositing,  but  by  much  water  which  arose  from  the 
melting  of  the  ice  far  back  from  the  margin.  The  general  mobility  of 
the  water,  as  contrasted  with  the  ice,  allowed  it  to  concentrate  its  activi- 
ties along  those  lines  which  favored  its  motion,  so  that  different  por- 
tions of  the  drift  were  not  affected  equally  by  the  water  of  the  melting 
ice. 

All  in  all,  it  will  be  seen  that  the  water  must  have  been  a  very  im- 
portant factor  in  the  deposition  of  the  drift,  especially  near  the  margin 
of  the  ice.  But  the  ice  sheet  had  a  marginal  belt  throughout  its  whole 
history,  and  water  must  have  been  active  and  effective  along  this  belt, 
not  only  during  the  decadence  of  the  ice  sheet,  but  during  its  growth 
as  well.  It  is  further  to  be  noted  that  any  region  of  drift  stood  good 
chance  of  being  operated  upon  by  the  water  after  the  ice  had  departed 
from  it,  so  that  in  regions  over  which  topography  directed  drainage 
after  the  withdrawal  of  the  ice,  the  water  had  the  last  chance  at  the 
drift,  and  modified  it  in  such  a  way  and  to  such  an  extent  as  circum- 
stances permitted. 


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Fig.  10.    Section  showing  relations  of  stratified  drift  (a),   till  (b),   and  beach  sands  and 
gravels  (c),  as  exposed  at  Winthrop  Harbor. 


There  are  no  clearly  defined  areas  of  stratified  drift  in  the  upland 
part  of  the  Evanston-Waukegan  region,  but  within  the  drift  ex- 
posures along  the  lake  cliff,  lenses  or  patches  of  stratified  drift  may 
be  seen  frequently. 

At  Winthrop  Harbor  the  section  represented  in  Fig.  io  is  exposed 
along  the  main  north-south  road.  The  stratified  drift  at  the  base 
was  deposited  beyond  the  ice  edge  during  its  advance,  or  during  some 
temporary  period  of  recession.  After  the  assorted  material  was  laid 
down,  the  ice  advanced  over  this  particular  area,  and  deposited  a 
layer  of  till.  The  sands  and  gravels  above  the  unstratified  drift  of 
the  section  are  beach  formations  of  the  Glenwood  stage  of  Lake 
Chicago. 


26 


THE    EVANSTON-WAUKEGAN    KEG  ION. 


I  BULL.  7 


Pig.  11.     Drainage  in  the  driftless  area.     The  absence  of  ponds  and  marshes 
is  to  he  noted.    (Courtesy  of  Wisconsin  Geol.  Nat.  Hist.  Surv.) 


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Fig.  12.    Drainage  in  a  glaciated  region,  Walworth  and  Waukesha  counties,  Wis.,  showing 
abundance  of  marshes  and  lakes.    (Courtesy  Wis.  Geol.  Nat.  Hist.  Surv.) 


ATWOOD.J 


THE   GEOLOGICAL    FORMATIONS. 


27 


Stratified  drift  covers  much  of  the  surface  below  an  altitude  of 
640  feet.  (See  topographic  maps.) 

To  appreciate  the  changes  which  glaciation  effected  in  this  region, 
it  may  be  pointed  out  that  both  the  topography  and  the  surface  ma- 
terial of  unglaciated  regions  are  very  different  from  those  of  this  re- 
gion. The  driftless  or  unglaciated  area  in  the  northwestern  part  of 
the  State  already  referred  to,  has  a  surface  shaped  almost  wholly  by 
running  water.  All  depressions  are  valleys  and  have  outlets.  The 
region  is  therefore  well-drained,  and  so  without  the  ponds,  marshes, 
etc.,  which  often  characterize  recentlv  glaciated  areas    (Figs,    n   and 

I2>: 

Unglaciated  surfaces  are  generally  overspread  by  a  mantle  of  soil 

and  earth  which  has  resulted  from  the  decomposition  of  the  underlying 

rock.     This  earthy  material  sometimes  contains   fragments  and  even 

large  masses  of  rock  like  that  beneath.     These  fragments  and  masses 

escaped  disintegration  because  of  their  greater  resistance,  while  the 

surrounding  rock  was  destroyed.    This  mantle  rock  grades  from  fine 

material  at  the  surface  down  through  coarser,  until  the  solid  rock  is 

reached,   the  upper  surface  of  the  rock  being  often   ill-defined    (Fig. 

13).     The  thickness  of  the  mantle  is  approximately  constant  in   like 

topographic   situations   where  the  underlying  rock  is  uniform.     The 

residual  soils  are  made  up  chiefly  of  the  insoluble  parts  of  the  rock 

from  which  they  are  derived,  the  soluble  parts  having  been  removed 

in  the  process  of  disintegration. 


Fig.  13.    Diagram  showing  the  relation  of  residual  soil  to  the  underlying  rock  from 
which  it  is  derived.    (Courtesy  of  U.  S.  Geol.  Surv.) 

With  these  residuary  soils  of  the  driftless  area,  the  mantle  rock  of 
glaciated  tracts  is  in  sharp  contrast.  Here,  as  already  pointed  out, 
the  material  is  diverse,  having  come  from  various  formations  and 
from  widely  separated  sources.  It  contains  the  soluble  as  well  as  the 
insoluble  parts  of  the  rock  from  which  it  was  derived.  In  it  there  is 
no  suggestion  of  uniformity  in  thickness,  no  regular  gradation  from 
fine  to  coarse  from  the  surface  downward.  The  average  thickness  of 
the  drift  is  also  much  greater  than  that  of  the  residual  earths.  Further, 
the  contact  between  the  drift  and  the  underlying  rock  surface  is 
usually  a  definite  surface.    (Compare  Figs.  8  and  13.) 


28  THE    EVANSTON-WAUKEGAN    REGION.  [BULr,.  7 


THE  PRESENT  SHORE  LINE. 
(by  j.  w.  goldthwait.) 

Evolution  Seen  in  Shore  Line  Topography. 

The  land  forms  peculiar  to  shore  lines  depend  for  their  existence 
upon  those  movements  of  the  waters  which  are  initiated  by  the  winds. 
If  there  were  no  winds,  such  a  lake  as  Lake  Michigan  would  be  prac- 
tically without  waves  and  currents,  a  dead,  inert  sheet  of  water;  and 
its  shores  would  be  without  strength  and  character.  Shore  forms, 
like  all  other  forms,  are  changing,  living  objects  in  so  far  as  solar 
energy  is  expended  upon  them  through  the  so-called  geological 
agents — in  this  case  waves  and  currents.  On  sea  shores  the  tides  are 
also  of  importance  in  determining  and  constantly  modifying  the  shore 
topography. 

On  a  day  when  the  air  is  calm  or  when  a  light  off-shore  breeze  is 
blowing  and  the  lake  is  smooth,  the  agents  just  mentioned  are  tempo- 
rarily inactive.  On  such  a  day  one  may  stand  on  the  bluff  overlooking 
Lake  Michigan  at  any  point  on  the  north  shore,  and  as  far  out  as  can 
be  seen  the  lake  water  is  unclouded  by  sediment.  At  the  base  of  the 
bluff  is  a  bare  beach  of  sand  or  gravel,  against  the  border  of  which 
the  small  waves  are  lapping  in  a  weak,  desultory  way.  It  is  scene 
of  inactivity.  At  such  a  time  the  evolution  of  shore  forms  would  not 
be  evident.  But  when  a  strong  east  wind  has  roused  the  waves  to 
violence,  whitecaps  dot  its  roughened  surface,  and  a  strong  surf  is 
breaking  near  the  shore  and  sweeping  back  and  forth  in  rhythmic 
fashion  at  the  base  of  the  cliff,  nearly  or  quite  concealing  the  beach 
platform  below.  The  waves  are  gnawing  into  the  base  of  the  bluff, 
exposing  the  fresh,  blue  clay,  where  formerly  may  have  been  a  turf- 
covered  slope.  From  the  face  of  the  bluff,  thus  steepened,  great  masses 
of  clay  may  be  seen  slipping  down  to  the  water's  edge,  where  they  are 
further  broken  up  by  the  waves  and  thoroughly  separated  into  the 
constituent  boulders,  gravel,  sand  and  mud.  Trees  toppling  from 
the  brink  of  the  bluff  emphasize  the  rapidity  of  the  process  (Plate 
III,  Fig.  A).  The  waters  of  the  lake  for  a  long  way  out  are  muddy 
with  suspended  sediment.  By  oblique  advances  and  retreats  of  the 
waves  upon  the  shore,  gravel  is  being  washed  up  and  down  the 
beach  in  zig  zag  fashion  along  the  shore.  It  is  an  easy  inference  that 
in  the  shallow  water  just  beyond,  sand  is  being  drifted  steadily  lee- 
ward. The  lake  is  now  in  action,  and  the  shore  form  in  process  of 
development.  One  returns  from  such  a  view  with  a  ready  belief  in 
doctrine  of  change  or  evolution  as  applied  to  shore  forms. 


GOLDTHWAIT  I 


THE   PRESENT    SHORE   LINE. 


29 


AGENTS  AT  WORK  ALONG  SHORE  LINES.* 

The  Waves — When  a  strong  wind  sweeps  across  the  surface  of  a 
body  of  water,  it  communicates  energy  which  sets  every  water  particle 
oscillating  in  an  approximately  circular  orbit — the  basis  of  the  phen- 
omenon which  we  call  a  wave.  In  the  normal  off-shore  wave,  or 
in  any  normal  wave  away  from  the  shore,  there  is  very  little  forward 
advance  of  the  water;  each  particle  returns  nearly  or  quite  to  its 
original  position,  so  that  the  wave  has  well  been  called  "a  traveling 
shape  of  water."  In  the  form  of  wave  known  as  the  swell,  which 
moves  in  deep  water,  outside  the  area  which  is  under  the  direct  influ- 
ence of  the  wind,  the  orbits  of  the  particles  of  water  are  closed. 
There  is  no  permanent  advance  of  the  water.  But  in  the  wind  wave, 
the  forward  movement  of  the  particle  is  always  slightly  in  excess  of 
the  return  movement,  so  that  each  particle  describes  a  spiral  rather 
than  an  ellipse,  and  there  is  generated  a  slow  current  which  moves  for- 
ward following  the  waves.     Figure  14  shows  how  the  particles  move 


Fig.  14.    Diagram  showing  the  movement  of  particles  in  a  wave.    The  waves 
are  moving  from  left  to  right. 


in  different  parts  of  a  wave,  forward  in  the  crest,  backward  in  the 
trough,  upward  in  front  of  the  crest  and  downward  behind  it.  The 
orbital  motion  of  the  particle  is  less  rapid  than  the  wind ;  the  advance 
of  the  wave  is  even  slower,  and  that  of  the  wind  driven  current  is 
still  slower.  By  transmission  downward,  these  motions  are  extended 
into  deep  water,  but  with  rapidly  diminishing  effect.  The  deeper 
the  water,  the  less  are  the  movements  embarrassed  by  friction  on  the 
bottom,  the  larger  will  be  the  waves  and  the  stronger  the  currents. 
On  the  open  ocean,  wind  waves  are  sometimes  fifty  feet  high  and 
1,500  feet  long,  measured  from  crest  to  crest;  but  these  are  excep- 
tional. On  Lake  Michigan  the  waves  exceptionally  attain  a  height 
of  twenty  feet. 

The  crest  of  a  wave  is  always  sharper  than  the  trough,  for  the  wave 
assumes  the  form  of  a  trochoid  curve,  such  as  is  described  by  a  point 
within  a  circle  which  rolls  on  a  horizontal  line.  (See  Figure  15  H.) 
The  sharpness  of  the  crest  is  exaggerated  when  the  wave  length  is 
shortened  or  its  height  increased.  Compare,  for  instance.  Figures 
15,  16,  17  and  18. 


*  In  the  preparation  of  what  follows  regarding  waves  and  their  work  the  writer  has  drawn 
freely  from  Gilbert's  paper  on  "The  Topographic  Features  of  Lake  Shores.  "  U.  S.  Geol.  Surv., 
5th  Ann.  Rept.,  pp.  69-123,  1885;  and  chapter  2  in  Fenneman's  "Lakes  of  Southeastern  Wiscon- 
sin, "  Wis.  Geol.  and  Nat.  Hist.  Surv.  Bull.  8,  1902. 


30 


THE    EVANSTON-WAUKEGAN    REGION. 


[bull.  7 


Fig.  15.  Series  of  particles  in  their  orbits.  The  circles  represent  the  orbits  of  the  particles 
which  revolve  from  left  to  right.  At  any  given  moment  each  particle  is  advanced  in  its  orbit 
54  degrees  more  than  its  neighbor  on  the  right.  The  curved  line  connecting  these  simultaneous 
positions  of  the  particles  represents  the  form  of  the  wave.    (After  Fenneman.) 


Fig.  16.    The  phasal  difference  of  the  particles  has  been  increased  from  45°  to  90°.    The 
crests  of  the  waves  thus  become  sharper.    (After  Fenneman.) 


Fig.  17.    The  orbits  have  been  increased  to  twice  their  former  size;  but  the  phasal 
difference  is  the  same  as  in  fig.  15.     (After  Fenneman.) 


Fig.  18.    By  an  increase  both  in  the  phasal  difference  of  the  particles  and  in  the  size  of 
the  orbits,  a  curve  is  developed,  suitable  for  breakers.    (After  Fenneman.) 


In  Figure  15  various  positions  of  a  series  of  neighboring  particles 
in  the  waves  in  their  respective  orbits  are  shown,  the  phasal  differ- 
ence of  the  particles  being  45 °.  The  surface  of  the  wave  which 
passes  through  these  particles  forms  a  low  trochoid  curve.  In  Figure 
16  the  wave  has  been  shortened  by  increasing  the  difference  in  phase 
of  the  particles  to  900  ;  and  the  trochoid  is  more  pronounced  in  form 
than  before,  with  sharper  crest  and  flatter  troughs.  In  Figure  17  the 
waves'  length  is  like  that  of  the  first,  but  the  amplitude  of  the  orbital 
motion  has  been  increased,  and  as  a  consequence  the  contrast  between 
the  crest  and  trough  exaggerated.  In  Figure  18  the  shortening  and 
increase  of  amplitude  has  gone  so  far  as  to  develop  a  trochoid  curve 
that  has  loops  in  place  of  cusps — the  condition  for  breaking  waves. 
White  caps  are  an  expression  of  such  a  curve  as  the  last,  developed 
when  the  amplitude  of  the  wave  is  increased  more  rapidly  than  its 
length  by  a  wind  of  fast  increasing  strength. 

When  a  wave  approaches  a  shelving  shore,  reaching  shallower  and 
shallower  water,  its  form  is  very  considerably  changed:  (1).  The 
wave  becomes  higher;  for  the  transmission  of  energy  to  a  smaller 
amount  of  water  gives  to  each  particle  an  increased  orbital ,  movement ; 
(2).  The  wave  is  shortened,  for  increased  friction  diminishes  the 
velocity  of  orbital  motion  of  every  particle,  and  this  means  a  greater 
differential   movement   between   the   neighboring   particles    (compare 


GOLDTHWAIT 


THE    PRESENT    SHORE   LINE.  31 


Figures  15  and  16;  (3).  The  crest  becomes  steeper  and  sharper,  the 
result  of  shortening  the  wave ;  and  (4)  the  crest  becomes  a  symmetri- 
cal, steeper  in  front  than  behind,  because  the  forward  motion  in  the 
crest,  where  the  water  is  deeper,  is  more  rapid  than  the  backward  mo- 
tion in  the  trough,  where  water  is  shallower. 

These  changes  of  form  become  more  and  more  marked,  finally  re- 
sulting in  the  breaking  of  the  wave.  The  crest  is  thrown  forward 
with  a  curling  front,  and  the  water  foams  and  tosses  with  the  con- 
fusion of  oscillatory  and  translatory  movements,  for  the  sudden 
plunge  of  the  broken  crest  starts  new  waves  of  translation  or  "soli- 
tary waves,"  which  are  quite  different  in  nature  from  waves  of  oscil- 
lation. In  the  wave  of  translation  each  particle  is  carried  forward  in 
a  semi-ellipse,  those  at  the  bottom  moving  as  far  as  those  at  the  sur- 
face. 

Waves  of  translation  are  very  efficient  in  sweeping  material  ashore. 
Since  breakers  usually  form  close  to  the  water's  edge,  translatory 
waves  are  usually  of  short  range  and  consist  merely  of  a  forward  dash 
or  "swash"  of  the  wave  to  the  crest  of  the  beach.  If,  however,  the  in- 
coming wind-waves  break  far  off  shore,  as  on  a  very  shallow  bottom, 
the  diminution  of  height  may  permit  them  to  re-form  in  conjunction 
with  the  translatory  waves,  and  to  run  ashore  until  finally  they  break 
again.  Translatory  waves,  where  uncombined  with  oscillatory  waves, 
are  easily  distinguished  by  their  extremely  broad  and  flat  troughs,  and 
narrow,  sharp  crests.  The  on-shore  dash  of  the  broken  wave  is  fol- 
lowed by  a  return  wash  of  the  water  down  the  beach  slope  to  the  point 
where  it  meets  the  next  incoming  wave  of  translation.  Thus  there  is 
between  the  breakers  and  the  water's  edge  a  zone  where  material  is 
shifted  back  and  forth  by  opposed  rhythmic  movements.  Under  dif- 
ferent conditions  of  shore  profile,  wave  force,  etc.,  either  the  inward 
or  the  outward  action  may  be  favored,  and  the  erosion  or  deposition 
determined. 

Undertow — The  return  flow  of  the  broken  wave  gives  rise  to  a  per- 
manent outgoing  movement  known  as  the  "undertow."  In  a  more 
comprehensive  way,  the  undertow  may  be  thought  of  as  the  means 
by  which  all  water  moved  ashore  by  the  wind-driven  currents  and  by 
the  waves  of  translation  finds  its  way  back  to  deep  water.  Instead  of 
being  a  steady  movement,  it  is  a  pulsating  one,  markedly  so  just  out- 
side the  breaker  line,  because  of  the  continual  passage  of  oscillatory 
waves  above  it,  and  the  alternate  cooperation  and  opposition  of  those 
oscillations.  Close  to  the  breaker  line,  indeed,  the  on-shore  transla- 
tory motion  may  counter-balance  the  undertow,  and  these  conditions 
are  favorable  for  deposition  of  material  from  both  the  off-shore  and 
the  on-shore  forces.  The  pulsating  nature  of  the  undertow  greatly 
increases  its  ability  to  transport  waste  seaward,  for  by  hundreds  of  re- 
peated jerks,  a  pebble  which  would  be  immovable  under  a  steady  cur- 
rent of  the  average  velocity  of  the  undertow,  may  be  carried  out  inch 
by  inch  to  a  considerable  depth.  Thus  it  is  that  while  the  average 
velocity  of  currents  along  the  Lake  Michigan  shore  would  permit 
them  to  carry  sand  no  farther  out  than  to  a  depth  of  about  36  feet, 
gravel,  which  may  be  suspected  to  have  been  carried  out  by  the  lake 


32  THE   EVANSTON-WAUKEGAN    REGION.  Lbull.  7 

currents,  is  found  much  farther  off  shore.  It  is  also  to  be  expected, 
of  course,  that  irregularity  of  the  lake  shore  will  lead  to  local  con- 
centrations of  the  outgoing  current. 

The  office  of  the  undertow  is  primarily  to  dispose  of  material  eroded 
by  the  waves ;  but  it  also  scours  the  submerged  platform  across  which 
the  waves  are  sawing  back  into  the  land:  Without  it,  of  course,  there 
could  be  no  inland  recession  of  a  shore. 

Shore  Current — Usually  the  storm  wind  does  not  blow  straight  on- 
shore, but  at  an  angle  to  it.  Consequently  the  waves  far  off  shore  are 
advancing  with  fronts  oblique  to  the  shore  line.  That  part  of  the 
incoming  wave  which  first  reaches  shallow  water  will  be  retarded, 
the  wave  front  being  bent  or  refracted  until,  by  the  time  the  wave 
breaks,  it  is  nearly  parallel  to  the  beach.  So  efficient  is  this  refraction 
that  with  winds  from  very  diverse  quarters  the  obliquity  of  the  surf 
to  the  shore  line  is  always  a  small  angle.  It  is  usually  enough,  how- 
ever, to  determine  a  marked  drift  along  the  shore,  called  the  "shore 
current."  This  is  the  great  agent  of  transportation  of  sand  and 
gravel  along  shore,  though  it  is  aided  in  this  work  by  the  waves 
themselves  in  the  zigzag  swash  and  return  flow  along  the  beach. 
Although  on  some  coasts  it  is  true  that  storm  winds  from  different 
quarters  frequently  reverse  the  direction  of  the  shore  current,  it 
nearly  always  happens  that  on  account  of  the  prevailingly  greater 
strength  of  wind  from  one  direction,  one  of  the  opposed  currents 
is  the  dominant  one. 

Development  of  Coastal  Topography. 

When  a  lake  is  first  formed  in  an  enclosed  basin,  or  when'  a  con- 
siderable change  in  level  brings  a  lake  into  a  new  position  against 
the  land,  the  waves  and  currents  find  a  coast  which  is  not  adjusted  to 
their  erosive  and  constructive  activity. 

The  coast  may  be  very  irregular  in  outline  and  ill  adapted  to  an 
organized  system  of  waves  and  currents.  This  is  particularly  the  case 
with  a  newly  formed  lake,  or  with  a  shore  which  has  been  produced 
by  the  submergence  of  a  river- sculptured  land  surface  (as  by  a  sink- 
ing of  the  land  with  reference  to  the  sea).  On  the  other  hand,  if  the 
shore  line  be  determined  by  a  rise  of  the  submerged  sea  floor  to  form 
a  shelving  coastal  plain,  or  if  the  lowering  of  the  level  of  a  lake  lays 
bare  a  smooth  lake  plain,  the  shore  may  have  a  simple  outline,  but  its 
profile  may  not  be  adjusted  to  the  waves.  Whatever  be  the  nature 
of  the  initial  shore  line,  whether  it  be  an  irregular  shore  of  depres- 
sions or  a  straight  shore  of  elevation,  changes  in  profile,  and  to  a 
greater  or  lesser  degree  in  horizontal  configuration  are  sure  to  be 
wrought  out  by  the  waves. 

CHANGES   IN    PROFILE. 

In  profile,  the  new  shore  may  be  steep,  and  the  undertow  may  thus 
be  favored,  so  that  more  loose  material  will  be  swept  off-shore  by  the 
waves  than  can  be  brought  in  by  on-shore  action.  Or  the  slope  of 
the  new  shore  may  be  gentle,  in  which  case  incoming  waves  will  be 
stronger  than  the  undertow,  and  more  material  brought  in  than 
is  swept  out.     In  either  case,  the  opposed  forces  will  tend  to  con- 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.  3. 


Fig.  A.    Receding  cliff  at  Gross  Point. 


Fig.  B.     Sand  dunes  at  Rogers  Park. 


GOLDTHWAIT. 


THE    PRESENT    SHORE   LINE.  83 


struct  a  profile  on  which  the  incoming  and  the  outgoing  of  beach 
gravel  and  sand  is  balanced — an  ideal  adjusted  curve  known  as  the 
"profile  of  equilibrium."  Once  gained,  this  profile  is  in  a  general  way 
stable.  Yet  it  is  subject  to  a  gradual  change  because  the  beach  ma- 
terial is  constantly  being  worn  out  and  scattered  far  off  shore,  and 
because,  with  progressive  change  in  horizontal  outline  of  the  shore, 
the  amount  of  waste  material  along   shore  is  continually   changing. 

The  latter  element  of  change,  the  variation  in  direction  and  rate 
of  "long-shore  drift"  (beach  gravel  and  sand),  is  a  consequence  of 
the  initial  irregularity  of  the  shore,  both  in  plan  and  in  profile.  Not 
only  will  the  shore  agents  seek  to  establish  a  balanced  profile,  but 
the  shore  currents  especially  will  so  distribute  the  beach  waste  as  to 
reduce  the  hvegularities  of  the  shore  by  cutting  back  the  headlands 
and  filling  in  the  bays.  A  closer  inspection  of  this  development  of 
shore  topography  may  now  be  made.  It  will  be  convenient  to  con- 
sider first  the  changes  wrought  in  profile  and  then  the  changes  in 
horizontal  configuration,  although  these  must  always  go  on  at  the 
same  time. 

The  Sea  Cliff — If  the  initial  slope  is  steeper  than  the  profile  of  equil- 
ibrium, the  waves  strike  the  shore  forcibly  and  cut  away  the  material 
at  the  waters'  edge,  while,  together  with  the  shore  currents  and  the 
undertow,  they  separate  and  carry  away  the  debris — the  coarser  part 
being  drifted  along  shore  and  the  finer  being  carried  in  suspension 
far  off  shore,  until  it  settles  in  deep  water.  The  debris  thus  gathered 
is  used  by  the  waves  as  a  tool  by  which  to  cut  away  the  base  of  the 
cliffs.  The  process  is  essentially  a  horizontal  sawing  at  the  water's 
edge,  whereby  a  submerged  terrace,  flatter  than  the  initial  slope,  is 
cut  backward  into  the  land,  and  the  coast  above  lake  level  is  steepened 
to  a  line  of  cliffs. 


,-ori:^ 


LAKE-LEVEL.-   nt;    U. 


Fig.  19.    Section  showing  how  a  cliff  and  wave-cut  terrace  is  developed. 
(Salisbury  and  AJden.) 

The  initial  profile  D  B  A  is  thus  gradually  changed  to  a  profile  D 
D  '  A  '.  The  wave  cut  D'  A',  instead  of  being  horizontal,  will  slope 
gently  off  shore,  because  its  outer  border  began  to  be  eroded  first 
and  because  the  wave  action  is  stronger  there.  The  width  and  the 
slope  of  the  cut  terrace,  the  depth  of  its  submerged  outer  border,  and 
the  height  of  its  upper  border  above  lake  level,  vary  according  to  the 

-3G. 


34  THE    EVANSTON-WAUKEGAN    REGION.  [bull.  7 

strength  of  the  wave  action,  the  time  during  which  the  waves  and 
currents  have  been  at  work,  and  the  strength  of  material.  The 
longer  the  process  goes  on,  the  broader  and  deeper  will  be  the  outer 
border  of  the  terrace.  The  greater  the  "fetch"  of  the  waves,  the 
farther  up  the  slope  can  erosion  extend,  and  the  higher  the  upper 
border  of  the  terrace  will  be.  On  abrupt  rocky  shores  the  terraces  are 
usually  narrow  and  steeply  inclined.  In  the  north  shore  district,  be- 
tween Evanston  and  Waukegan,  the  platform  at  the  base  of  the  clay 
bluffs  has  a  gentle  slope  and  rises  usually  three  or  four  feet  above 
lake  level.     (See  Plate  III,  Fig.  A,  and  Plate  IV,  Fig.  A.) 

The  recession  of  these  clay  bluffs  is  accompanied  by  land  slips  of 
considerable  size,  particularly  in  the  spring,  when  the  thawing  of  the 
frozen  clays  and  the  percolation  of  water  supplied  by  spring  rains 
lubricates  the  structure,  so  that  great  blocks  of  the  oyer-steepened 
cliff  part  and  slide  downward  toward  the  lake.  Fresh  land  slides 
of  this  kind  often  form  a  sod-covered  terrace  or  group  of  step-like 
terraces  along  the  bluffs,  the  bare  clay  surface  above  the  terrace  fre- 
quently showing  grooves  where  stones  or  roots  of  the  loosened  block 
scraped  against  the  opposite  side  of  the  slipping  plane  during  the  dis- 
placement. Frequently,  also,  the  loosened  and  lubricated  clay  slides 
down  the  cliff  face  in  a  plastic  condition,  forming  steep  cones  of 
sticky  mud;  but  wave  action  soon  trims  them  away,  steepening  the 
lower  part  of  the  cliff,  eating  back  into  the  more  solid  landslide  block, 
and  thus  favoring  a  renewal  of  the  slipping.  Successive  blocks  are 
thus  pulled  down  by  gravity  as  the  waves  cut  inland.  Much  material 
also  creeps  down  the  steep  cliff  face  in  small  amounts,  and  very  much 
is  washed  down  by  rain,  developing  innumerable  gullies  from  which 
the  waste  is  spread  out  on  the  beach  in  fan-like  deposits.  (See  Plate 
XL) 

It  must  not  be  thought,  however,  that  ^ie  shore  terrace  is  wholly 
a  wave-cut  form.  It  is  commonly  covered  with  a  sheet  of  gravel  and 
sand  called  the  beach,  and  if  it  borders  deep  water,  its  outer  margin 
is  usually  extended  by  deposits  of  waste  carried  out  by  the  undertow. 


Pig.  20.    Cross  section  of  a  sea  cliff  with  a  cut-and-built  terrace. 

So  long  as  the  shore  line  is  advancing  into  an  upland  which  slopes 
toward  the  lake,  as  is  quite  generally  the  case  along  the  north  shore, 
the  shore  cliffs  will  of  necessity  be  increasing  in  height.  In  other 
words,  the  cliff  face,  from  which  waste  is  being  swept  to  the  lake  by 
land  slides,  creeping,  and  rain-wash,  is  constantly  increasing  in  area, 
and  thus  the  rate  of  supply  of  waste  is  increasing.     A  critical  point 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.  4. 


Fig.  A     Cliff  and  beach  near  Fort  Sheridan.     |C  curtesy  of  C  &  N\  W.  Ry 


Fig.  B.     Lake  cliff  at  Racine.  Wis.,  near  Rucine  College.    The  waves  have  continued  to 
encroach  upon  the  land  in  spite  ol  the  piers.     [Courtesy  of  C   cV  X.  W.  Ry.  I 


goldthwaitJ  THE    PRESENT   SHORE   LINE.  35 

may  thus  be  reached  when  the  supply  of  waste  begins  to  exceed  the 
capacity  of  the  waves  and  currents  to  transport  it.  The  waves  and 
currents  then  become  overloaded,  the  beach  on  the  terrace  is  broadened 
and  thickened  by  deposition  of  waste,  and  the  cliffs  retreat  with  less 
and  less  rapidity.  Meanwhile,  the  terrace  has  been  broadened  and 
deepened  until  its  outer  edge  may  be  as  low  as  the  level  of  effective 
erosion  by  waves  and  currents,  a  limit  known  as  "wave  base." 
Farther  retreat  of  the  cliffs  will  go  on  only  so  fast  as  the  material 
of  the  beach  is  worn  out  by  the  slow  grinding  process,  and  the  terrace 
will  become  flatter  as  more  and  more  of  it  is  reduced  to  the  wave 
base.  So  it  comes  about  that  the  most  rapid  retreat  of  the  lake  cliff 
is  usually  in  the  early  stages  of  its  development.  It  may  then  possess 
a  simple  wave-cut  platform  from  which  the  material  is  carried  as  fast 
as  it  is  fed  down  the  cliffs.  Such  bare  clay  platforms  may  be  seen 
occasionally  along  the  north  shore  where  cliff  recession  is  most  active, 
but  usually  the  platform  is  covered  with  at  least  a  thin  veneer  of  sand 
and  gravel.  At  those  points  where  the  till  includes  more  bowlders  and 
pebbles  than  usual,  the  beach  is  more  gravelly  than  where  the  till  con- 
sists almost  entirely  of  clay.  The  beach  reflects  somewhat  imperfectly 
the  composition  of  the  associated  cliffs. 

The  Beach  Ridge — When  the  coastal  slope  is  flatter  than  the  profile 
of  equilibrium,  the  undertow  is  weaker  than  the  on-shore  movement  of 
translatory  waves;  hence  material  is  shifted  shoreward  and  cast  up 
at  or  near  the  water's  edge  in  such  a  way  as  to  steepen  the  slope.  The 
profile  of    typical  beach  has  a  gentle  sigmoid  curve,  the  back-slope  of 


Fig.  21.    Cross  section  of  a  beach. 


the  ridge  being  short,  steep  and  convex  upward,  while  the  front  slope 
(below  the  convex  curve  of  the  ridge)  is  long,  gentle  and  concave — 
the  concavity  expressing  an  equilibrium  between  the  opposed  forces. 
Because  the  on-shore  wave  action  increases  rapidly  toward  the  water's 
edge  to  the  detriment  of  the  undertow,  the  deposition  becomes  rapidly 
greater  near  that  line  and  the  resulting  slope  is  increasingly  steeper — 
that  is,  concave.  But  the  crest  of  the  ridge  and  its  back-slope  are  de- 
termined chiefly  by  the  angle  at  which  the  beach  material  comes  to  rest 
when  cast  up  out  of  reach  of  the  waves. 

It  must  not  be  thought,  however,  that  slope  is  the  only  factor  which 
determines  whether  waves  and  currents  of  a  gfiven  strength  will  build  a 
beach  or  cut  a  terrace  and  cliff.  Load  (amount  of  sand,  gravel,  etc. 
handled  by  the  waves)  is  quite  important.  And,  as  will  be  brought  out 
later,  the  amount  of  load  depends  largely  upon  the  strength  of  shore 
currents.  Much  more  waste  may  be  brought  to  a  given  place  by  drift 
of  material  along  the  shore  than  by  the  on-shore  sweep  of  translatory 


36  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

waves.  Beach  ridges  may  therefore  accumulate,  even  on  moderately 
steep  slopes,  if  the  supply  of  shore  drift  is  too  great  for  the  undertow  to 
sweep  away. 

Beach  ridges  are  common  along  the  abandoned  shorelines  of  the 
Evanston- Waukegan  district,  to  be  described  in  pages  54-68.  Some  of 
them  were  doubteless  true  beaches,  built  by  on-shore  transportation  in 
shallow  water;  but  the  more  conspicuous  ridges  seem  to  have  been 
great  barriers  or  bars  of  the  sort  presently  to  be  described  and  to  be 
attributed  mainly  to  long  shore  transportation.  Occasional  secondary 
ridges  often  with  faint  crests,  which  lie  on  the  lakeward  slope  of  the 
main  ridges  (e.  g.  the  lower  ridges  on  the  campus  at  Northwestern 
University)  seem  to  have  been  normal  shallow  water  beaches. 

The  Barrier — When  the  initial  slope  is  excessively  flat  the  incoming 
waves  break  some  distance  off-shore  and  there  grows  up  along  the 
breaker  line  a  reef  or  "barrier."  The  material  accumulated  in  it  is 
brought  partly  from  off-shore  by  the  incoming  surf  and  partly  from  the 
land  by  the  outgoing  undertow.  The  barrier,  then,  like  the  ordinary 
beach  ridge  may  be  looked  upon  as  the  result  of  the  effort  of  the  pre- 
dominant on-shore  movement  to  steepen  the  slope  to  the  curve  of 
equilibrium,  it  being  necessary  in  this  case  that  the  beach  ridge  be 
built  off-shore  instead  of  at  the  water's  edge,  if  a  curve  of  sufficient 
steepness  is  to  be  constructed  within  the  range  of  the  waves.  Again, 
however,  the  long-shore  supply  of  waste  must  be  considered,  as  well  as 
on  and  off-shore  movements  of  beach  material.  It  is  believed  that 
shore  drift  currents  are  often  of  great  importance  in  the  accumulation 
of  barriers,  for  the  breaker  line  is  a  line  of  greatest  agitation  of  the 
water,  sand  and  gravel  is  constantly  being  danced  up  and  down  below 
the  breakers,  and  the  shore  currents,  which  would  be  powerless  to 
move  such  coarse  material  if  it  were  at  rest  on  the  lake  bottom,  can  shift 
it  very  considerably  by  repeated  jerks  while  it  is  temporarily  in  suspen- 
sion. In  the  protected  water  lagoon  behind  the  barrier,  sediment 
swept  from  the  land  by  storms  or  from  the  lake  by  currents  may  be 
deposited.  Vegetation  is  likely  to  gain  possession  of  this  lagoon  and 
slowly  to  convert  it  into  a  marsh  or  peat  bog  (Fig.  22). 

So  long  as  the  supply  of  material  to  a  beach  or  a  barrier  is  constant, 
its  form  will  be  maintained  in  spite  of  the  loss  of  material  by  attrition 
and  by  off-shore  transportation.  It  may  be  that  the  supply  by  shore 
drift  on  the  outer  side  will  exceed  the  loss,  in  which  case  the  reef  will 
build  slowly  forward  into  the  lake.  More  frequently,  however,  the 
supply  fails  to  keep  pace  with  the  loss,  especially  where  sand  is  blown 
inland  from  the  beach  by  strong  on-shore  winds,  forming  a  line  of 
marching  dunes,  which  are  followed  consistently  by  the  beach  or 
barrier  itself.  So  it  happens,  sooner  or  later,  that  a  barrier  is  beaten 
back  across  its  lagoon,  in  which  it  is  likely  that  considerable  swamp 
deposits  have  already  been  formed  (see  Fig.  22).  The  line  of  reefs, 
reaching  the  main  land  shore  is  then  replaced  by  the  beach  ridge,  and 
finally,  if  erosion  continues  to  predominate,  by  a  line  of'  receding 
cliffs. 


goldthwait.]  THE    PRESENT    SHORE   LINE.  37 


'-  /    ' ""  <  ~  v  ~     .  x  ~  ^  /-^/  ^  -  ^s     ^^^^^^^^^^^     J     /"  >  -^ =— : — - — 

Fig.  22.  Cross  sections  of  a  barrier.  In  the  lower  figure  the  barrier  has  moved  inland,  part 
way  across  a  marshy  lagoon,    (b)  barrier;  (1)  lagoon;  (m)  marsh;  (p)  peat;  (d)  dune. 

The  life  history  of  a  barrier  beach  is  finely  illustrated  on  the  New 
Jersey  coast.  (See  Figure  23.)  The  heavy  surf  of  the  Atlantic 
ocean  running  ashore  on  the  low  shelving  coast  has  cast  up  a  long  line 
of  barrier  breaches  a  few  miles  off  shore.  At  Atlantic  City  the  barrier 
is  a  mile  broad  and  constantly  growing  on  its  seaward  side,  under  the 
excessive  supply  of  shore  drift.  Hotels  along  the  beach  have  been 
moved  forward  at  times  in  order  to  keep  near  the  ocean  front.  Farther 
north,  near  Barnegat  Bay,  the  barrier  has  retreated.  Here  the  supply 
of  shore  drift  is  not  sufficient  to  counterbalance  the  waste  lost  by 
attrition,  by  off-shore  scattering  and  by  the  construction  and  mainten- 
ance of  dunes,  which  are  marching  inland  across  the  salt  marshes  of  the 
broad  lagoon.  On  the  outer  side  of  the  beach  each  storm  exposes  and 
gnaws  back  the  edge  of  a  stratum  of  tide-marsh  deposit,  a  compact  mass 
of  mud  and  eel-grass — the  former  lagoon  deposits  across  which  the 
beach  is  being  pushed.  The  lagoon  narrows  northward,  toward  Point 
Pleasant,  where  the  barrier  joins  the  low  mainland.  Thence  northward 
for  about  15  miles  to  Long  Branch,  the  barrier  is  replaced  by  a  line  of 
low  sea-cliffs  which  are  receding  so  rapidly  during  storms  as  to  ser- 
iously endanger  property  along  the  shore.  Erosion  here  is  in  excess 
of  deposition ;  the  barrier  has  been  beaten  inland,  worn  out  and  replaced 
with  bluffs. 

The  ultimate  form  of  any  shoreline,  therefore,  is  normally  the  cliff 
and  terrace.  If  the  water  is  deep,  cliffs  develop  at  once,  and  are  main- 
tained so  long  as  no  abnormal  supply  of  load  is  brought  by  shore-drift 
currents.  If  the  water  is  shallow,  a  beach  or  a  barrier  is  first  thrown  up 
to  establish  the  profile  of  equilibrium ;  but  if  no  excessive  load  is 
brought  by  'long- shore  currents,  the  barrier  is  gradually  beaten  inland 
and  replaced  by  the  sea-cliff. 

Among  the  abandoned  shore  lines  of  the  Evanston  district,  the 
great  ridges  of  the  Glen  wood,  Calumet  and  Toleston  stages,  described 
in  pages  54-66,  may  be  regarded  as  barriers,  built  far  off-shore,  partly 
by  the  on-shore  sweeping  of  waste  and  partly  by  'long-shore  currents. 
The  great  Ridge  avenue  bar  in  Evanston  is  as  good  an  illustration  as 
any.    (See  pp.  61-63  an^  the  rnap,  Plate  VI.)    The  absence  of  barrier 


38 


THE    EVANSTON-WAUKEGAN    REGION. 


[bull.  7 


Pig.  23.    Outline  map  of  New  Jersey  showing  the  shore  line  with  its  retreating  barriers. 

beaches  along  the  present  shore  of  Lake  Michigan  may  be  attributed 
to  the  mature  condition  reached  by  the  lake  in  the  long  interval  since 
its  higher  stages.  The  present  lake  cliffs  are  comparable  in  their  devel- 
opment to  those  of  the  Long  Branch  district. 


CHANGES   IN   HORIZONTAL   CONFIGURATION. 

Spits,  Bars  and  Hooks — The  changes  wrought  in  the  horizontal  con- 
figuration of  the  shore  are  closely  associated  with  the  activity  of  'long- 
shore currents,  but  they  cannot  be  separated  from  the  work  of  waves 
and  undertow.  It  is  usually  true  that  along  an  initially  irregular  shore 
the  headlands  present  steeper  slopes  than  the  re-entrants.     Moreover, 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PL  5. 


Fig.  A.    Pier  and  beach  near  county  line  showing-  effect  of  southward  drift. 


Fig.  B.    Bar  at  mouth  of  ravine  near  county  line. 


OLDTHWAIT. 


THE    PRESENT    SHORE   LINE. 


;*9 


the  exposure  to  wave  action  is  greater  on  the  headlands ;  hence  the 
usual  development  of  the  eroded  sea-cliff  on  the  salients,  and  of  the 
beach  ridge  or  the  barrier  in  the  re-entrants  of  the  coast. 

The  wasting  headlands  supply  beach  material  for  the  shore  currents 
to  drift  into  the  re-entrants,  where  it  may  be  cast  up  as  a  "pocket-  or 
bay-head  beach,"  similar  to  the  beach  formerly  accounted  for  by 
excessive  on-shore  action.  With  a  constant  excess  of  supply  of  shore- 
drift,  such  a  beach  will  grow  continually  on  its  outer  border.  If  it  is 
built  up  across  the  mouth  of  a  stream,  it  may  form  either  a  continuous 
bar,  which,  except  during  floods,  is  increased  by  the  waves  (a  condition 
illustrated  by  Plate  V,  Fig.  B)  or  a  discontinuous  bar,  through  which 
a  channel  is  maintained  by  the  stream,  is  formed  (the  case  of  Petti- 
bone  Creek  and  others  of  its  size,  Plate  XII).  The  outlet  beach  is 
always  at  the  farther  end  of  the  bar  as  viewed  in  the  direction  of  the 
shore-drift  current,  because  the  stream  is  diverted  to  leeward  by  the 
drift.  If  the  beach  grows  outward  by  continual  deposition  on  its  sea- 
ward side,  the  stream  is  correspondingly  extended,  not  straight  out 
to  the  lake,  but  obliquely,  indicating  a  constant  response  to  the  deflec- 
tive force  of  the  shore-current.  Thus  in  the  map  (Fig.  24)  streams 
of  the  Long  Island  shore  have  been  extended  across  the  growing 
sand  beaches  in  deflected  courses  (e.  g.  the  stream  behind  West 
Meadow  beach). 


Crane^Neck  _                       jr~# 

Pt       <^-^^-^3^    -*>* 

W^C^y 

^\  *#'4\ 

iS    ^L^v. 

■C 

?  =5 ^  gfc 

4 
& 

e>*        §fr*Ji* 

0"N 

•Mr 

>{-'-" 

y" 

^5=        'fjs^/'- 

O                       1                        %                      3  mlUt 

^  '^H^€'^-"' 

'll^ 

Fig.  24. 


Map  of  a  part  of  the  north  shore  of  Long  Island  (sketched  from  the  Islip, 
N.  Y.,  sheet  of  the  IT.  S.  Geol.  Surv.) 


40  THE    EVANSTON-WAUKEGAN    REGION.  [bull.  7 

Sooner  or  later  the  deflected  stream,  especially  if  it  be  a  small  one, 
is  likely  to  be  blocked  at  its  mouth  by  thegrowthof  the  terroce.  Its 
water  then  reaches  sea  or  the  lake  by  percolation  through  the  terrace 
gravels. 

North  of  Waukegan  many  streams  follow  deflected  courses  behind 
the  beach  ridges  of  the  extinct  lake  stages.  As  the  lake  has  fallen  in 
level,  from  stage  to  stage,  these  streams  have  incised  themselves  along 
the  deflected  courses,  excavating  valleys  which  run  parallel  to  the 
shorelines  for  long  distances.  Deflected  courses  are  rare  and  fragment- 
ary along  the  present  shore,  however,  because  of  the  absence  of  spits 
and  bars  of  any  considerable  length ;  but  the  position  of  the  mouths  of 
such  streams  as  Pettibone  Creek  and  Little  Dead  River,  near  the  south 
end  of  the  obstructing  bars,  indicates  the  deflecting  tendency  of  the 
southerly  drift  currents. 

It  is  obvious  that  shore  currents  collecting  waste  from  the  eroded 
headlands  and  moving  along  in  a  wind-driven  course  will  fail  to  con- 
form in  detail  to  any  considerable  irregularity  of  the  shore,  but  will 
extend  off  in  a  gentle  curve,  thus  directing  the  shoredrift  out  into 
deeper  water,  where  it  comes  to  rest  as  a  submerged  reef. 

The  greatest  deposition  is  of  course  nearest  the  source  of  supply, 
much  of  the  coarser  material  being  dropped  close  to  the  headland, 
while  the  finer  is  swept  farther  on  before  it  comes  to  rest  at  the  end  of 
the  reef.  As  the  train  of  waste  is  built  outward,  it  is  also  built  up  by 
the  overloaded  waves  (along  the  line  of  storm  breakers  as  already 
described  for  the  barrier)  and  thus  becomes  a  "spit,"  whose  profile  is 
like  that  of  the  barrier  beach,  described  on  pages  36-37.  By  continued 
growth,  the  spit  becomes  a  ubar,"  reaching  so  far  across  the  bay  as 
nearly  or  wholly  to  enclose  it  (e.  g.  Stony  Brook  Harbor,  in  Fig.  24). 
No  hard  and  fast  distinction  can  be  made  between  a  spit  and  a  bar; 
they  are  different  stages  of  development  of  a  single  form.  Nor  can  a 
bar  be  distinguished  wholly  from  a  barrier,  for  in  neither  of  these 
forms  is  the  constructive  agent  a  single  and  independent  one.  It  is 
convenient,  however,  to  think  of  the  barrier  as  constructed  chiefly  b"y 


ws 


Fig.  25.     Sketch  map  showing  a  bay  enclosed  by  a  pair  of  overlapping  bars.    The 
arrows  indicate  the  direction  of  wind  driven  currents. 

on-shore  action  and  the  bar  by  'long-shore  drift.  Since  headlands  split 
the  wind-driven  currents  so  that  on  the  two  sides  of  the  bay  the  shore- 
drift  moves  in  converging  or  even  in  opposed  directions,  it  commonly 


(JOLDTHWAIT. 


THE    PRESENT    SHORE   LINE. 


41 


happens  that  spits  are  built  out  toward  each  other,  and  the  bay  is 
finally  inclosed  by  the  union  of  them,  or,  more  frequently,  the  overlap- 
ping of  one  by  the  other.  Since  the  strongest  surf  and  shore  currents 
come  with  wind  in  one  quarter,  and  the  currents  on  the  two  sides  of  a 
bay  are  unequal,  one  spit  commonly  experiences  more  rapid  growth 
than  the  other.  From  the  greater  exposure  of  the  spit  on  the  windward 
shore  of  the  bay,  it  tends  to  hug  the  shore  more  closely  than  its  neigh- 
bor ;  consequently  when  the  two  overlap  the  windward  spit  or  bar  is 
always  the  outer  one. 

The  free  end  of  a  growing  spit  is  always  subject  to  deflection  during 
storms  when  the  wind  comes  from  a  quarter  other  than  the  prevailing 
one. 


Fig.  26.    Sketch  map  showing  the  development  of  a  hooked  spit. 


Suppose,  for  instance,  that  the  strong  winds  come  prevailingly  from 
the  northeast ;  a  spit  will  be  built  toward  the  southwest  from  the  head- 
land in  Fig.  26  by  the  prevailing  shore  currents.  If,  after  the  spit  has 
grown  out  a  certain  distance,  it  comes  under  the  influence  of  a  strong 
southeast  wind  (B)  the  shore  current  will  be  deflected  in  such  a  way 
that  the  point  of  the  spit  will  be  turned  inward,  forming  a  hook.  With 
the  return  of  ordinary  conditions,  the  northerly  shore  current  will  be 
destroyed,  construction  of  the  spit  will  go  on  as  at  first  until  another 
change  in  quarter  of  a  storm  wind  repeats  the  deflection  and  a  new 
hook  is  formed  beyond  the  first.  A  long  series  of  hooks  may  thus  be 
constructed  along  the  growing  end  of  the  spit.  This  is  remarkably 
illustrated  by  Rockaway  Beach,  near  New  York  City   (see  Fig.  27). 


42 


THE   EVANSTON-WAUKEGAN    REGION. 


[bull.  7 


Pig.  27.    Outline  map  of  Rockaway  Beach,  Long  Island. 

Sandy  Hook,  outside  New  York  Harbor,  is  another  good  example 
of  a  hooked  spit,  built  by  heavily  laden  shore  currents, 
which  run  northward  from  the  cliffs  near  Long  Branch, 
New  Jersey  (Fig.  28).  By  continued  growth  on  its  outer 
side  and  by  the  shifting  of  dunes,  it  has  gained  a  breadth 
of  over  half  a  mile  near  its  northern  end.  Two  branch  spits  on  its 
western  or  bay  side,  point  significantly  toward  the  south,  indicating 
that  the  shore  drift  on  that  side  is  a  southward  one,  exactly  opposite 
to  the  northward  drift  of  the  ocean  side.  This  is  a  normal  feature,  to 
be  expected  on  any  well  developd  hook,  as  is  obvious  when  the  position 
of  the  main  hook  relative  to  the  bay  and  the  consequent  fetch  of  the 
bay  waves  from  different  quarters  is  considered.  The  main  spit  in  the 
case  of  Sandy  Hook  incloses  a  bay  at  its  southeast  corner.  While  a 
southeast  storm  would  favor  active  drifting  of  beach  material  north- 
ward along  the  Atlantic  border  of  the  hook,  it  would  not  stir  the  water 
on  the  bay  side  except  so  far  as  the  ocean  waves  rounded  the  promon- 
tory and  were  refracted  through  a  large  arc  as  they  ran  southward  up 
the  bay.  To  the  extent  that  this  occurs,  the  drift  of  material  along 
the  bay  side  of  Sandy  Hook  would  be  southward.  A  southwest  wind 
likewise  would  be  quite  as  inefficient  in  determining  the  drift  along  the 
bay  side,  because  there  would  be  almost  no  fetch  for  the  waves,  and  the 
shore  under  consideration  would  be  protected  from  the  wind  by  the 
highlands  of  Navesink.  A  west  or  northwest  wind,  on  the  other  hand, 
would  have  the  advantage  of  blowing  the  length  of  the  bay  and  would 
clearly  produce  the  dominant  short  drift — one  toward  the  south.  From 
the  very  conditions  under  which  great  hooked  spits  are  constructed, 
therefore,  minor  branches  on  their  protected  side,  if  developed  at  all, 
extend  in  opposite  direction  to  the  main  spit. 

Thus  it  came  about  in  one  of  the  extinct  stages  of  Lake  Michigan, 
when  the  lake  stood  about  35  feet  higher  than  now,  and  the  great  Ridge 
Avenue  barrier  in  the  Evanston  district  enclosed  a  broad  bay  (called 
the  "Wilmette  embankment"  on  the  map,  Plate  VI),  that  two  or  three 
branch  hooks  were  built  out  on  the  bay  side  of  the  barrier  by  currents 
running  northward — just  opposite  to  the  southward  flowing  currents 


GOLDTHWAIT.J 


THE    PRESENT   SHORE    LINE, 


43 


%0 


Fig.  28.    Sketch  map  of  Sandy  Hook,  N.  J. 


of  the  open  lake.  The  largest  of  these  secondary  hooks  lies  west  of 
Rogers'  Park.  Another  diverges  from  the  main  ridge  near  the  Evan- 
ston  golf  club  grounds.  These  repeat,  in  miniature,  the  type  of  spit 
illustrated  at  Spermaceti  Cave  on  the  inner  side  of  Sandy  Hook  (see 
Fig.  28).  A  comparison  of  Fig.  28  and  Plate  VI,  in  this  detail,  will 
be  found  instructive. 


44  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

In  the  early  high-level  stages  of  Lake  Michigan,  described  on  pages 
54-68,  beach  ridges,  barriers,  bars  and  spits  were  extensively  devel- 
oped;  for  the  original  shore  of  the  lake,  determined  by  glacial  topo- 
graphy was  very  irregular,  both  in  plan  and  in  outline,  and  ill-adapted 
to  wave  work.  Whenever  the  slope  was  deficient  or  the  supply  of  'long- 
shore drift  excessive,  beach,  ridges,  bars  and  similar  forms  were  built. 
But  as  time  went  on,  the  shores  were  smoothed  and  straightened  by  the 
waves,  so  as  to  correct  the  deficiencies  in  contour  and  profile,  beach 
ridges  were  superseded  by  shore  cliffs  as  the  lake  began  a  steady  ad- 
vance on  the  land.  The  present  shore,  therefore,  exhibits  no  beach 
ridges,  bars  or  barriers.  The  lake  has  outgrown  the  tendency  to  con- 
struct them,  in  its  successful  development  of  a  line  of  mature  cliffs. 

DUNES. 

Sand  dunes,  while  commonly  associated  with  shore  lines,  are  very 
frequently  developed  independently  of  them.  The  conditions  for  their 
growth  are  wind,  a  constant  supply  of  sand,  which  is  sometimes  dry, 
and  the  absence  of  a  cover  of  vegetation.  On  deserts,  like  the  Sahara, 
the  third  condition  is  made  possible  by  an  arid  climate;  while  the  sand 
is  supplied  by  shrunken  rivers  and  crumbling  sandstone.  But  even  in 
a  humid  climate  like  that  of  the  Great  Lake  region,  dunes  may  accum- 
ulate near  shores  where  the  supply  of  sand  by  shore  currents  is  very 
rapid  and  the  exposure  to  wind  is  great.  In  such  places  the  wind  is 
able  to  sweep  the  sand  up  from  the  beach  faster  than  vegetation  can 
establish  a  protective  cover. 

Sand  is  the  chief  constituent  of  beaches,  for  clay  is  extracted  bv 
waves  and  currents  and  swept  far  off  shore  in  suspension,  while  peb- 
bles are  rapidly  ground  down  in  process  of  transportation  along  shore. 
The  well-rounded  forms  of  beach  pebbles  testify  to  this.  Sand  itself 
is  relatively  indestructible  because  each  grain  in  the  beach  is  surrounded 
by  a  thin  film  of  water  held  to  it  by  capillary  attraction.  When  struck 
a  blow  by  a  breaking  wave,  therefore,  each  grain  is  shielded  from  its 
neighbors  by  a  minute  but  efficient  cushion.  Without  capillary  at- 
traction, sand  would  be  far  more  easily  worn  out,  beaches  would  be 
relatively  rare,  and  the  great  strata  of  sandstone  which  mark  long 
periods  of  earth  history  would  be  wanting.  It  is  only  when  the  sand  on 
the  beach  dries  that  the  wind  is  effective  in  lifting  and  transporting  it. 
Periodic  drying  is  possible  along  the  sea  border,  where  the  ebb  of  the 
tide  lays  bare  the  beach  twice  every  day.  It  is  less  favored  on  lake 
shores,  because  of  relative  stability  of  lake  waters.  But  of  course  the 
beach  cast  up  by  a  great  storm  becomes  in  part  a  dry  sand  ridge  during 
trie  succeeding  period  of  less  active  surf  and  it  may  then  supply  the 
sand  necessary  for  dunes.  The  fact  that  dunes  may  accumulate  about 
lideless  bodies  of  water  like  the  Great  Lakes  was  expressed  as  an  un- 
expected discovery  by  Edward  Desor  in  his  report  of  the  surface 
deposits  about  the  Upper  Peninsula  of  Michigan  in  1850.* 


*  Report  of  Edward  Desor  to  Messrs.  Foster  and  Whitney,  "Report  on  the  Geology  of  the 
Lake  Superior  Land  District."  Part  II.  chapter  XVI;  Senate  Exec.  Doc.  No.  4.  1851.  The 
writings  of  Desor  and  Whittelsey  in  this  report  are  of  great  interest  and  show  a  remarkably 
clear  appreciation  of  shore  line  topography. 


GOLDTHWAIT. 


THE   PRESENT    SHORE   LINE.  45 


With  a  strong  off-shore  wind,  beach  sand  may  be  blown  into  the 
lake,  to  be  again  handled  by  the  waves  and  currents.  But  with  an  on- 
shore wind  the  sand  is  swept  in  beyond  the  reach  of  the  waves,  accum- 
ulating in  low  mounds  about  any  obstructions  such  as  stones,  bushes, 
or  clumps  of  juniper.  Thus  started,  the  dune  is  sufficient  cause  for  its 
own  growth,  for  the  passing  sand  is  accumulated  in  the  still  air  on  its 
leeward  side  as  fast  as  it  is  eroded  from  the  windward  side.  It  is  a 
significant  fact  that  dunes  are  much  larger  and  much  more  extensively 
distributed  on  the  east  side  of  Lake  Michigan  than  on  the  west,  be- 
cause the  prevailing  winds  here  are  west  winds,  and  the  strong  east 
winds  on  which  the  dunes  of  the  west  shore  must  depend  for  growth 
are  prevailingly  storm  winds,  accompanied  by  rain,  which  wets  the 
beach  and  keeps  the  sand  in  place.  On  the  east  side  of  Lake  Michigan, 
especially  near  its  southern  end,  to  which  sand  is  eventually  swept  from 
the  whole  of  the  shore,  the  dry  west  winds  have  heaped  up  great  num- 
bers of  dunes,  ranging  in  height  up  to  200  feet.  In  Dune  Park,  Indi- 
ana, the  dunes  may  be  seen  moving  inland  across  a  forested  area,  bury- 
ing and  killing  trees,  and  also  moving  off  from  previously  buried  for- 
ests, leaving  the  dead  trunks  as  mere  skeletons.  A  famous  instance 
of  dune  migration  is  that  of  the  Kurische  Nehrung,  a  long  sandbar 
off  the  north  coatst  of  Germany,  where  a  dune  ridge  within  historic 
times  marched  over  a  church,  burying  it  for  30  years,  at  the  end  of 
which  time  it  was  gradually  uncovered. 

Dunes  are  limited  in  height  by  the  great  velocity  of  upper  air  cur- 
rents, to  about  200  feet.  Their  on-shore  march  is  also  limited  by  the 
fact  that  it  is  attended  by  the  attrition  of  the  sand  and  the  scattering 
over  a  wider  area. 

Dunes  occur  in  the  north  shore  district  along  the  beach  between  Wau- 
kegan  and  the  State  line,  and  in  less  notable  form  at  other  points,  as 
will  presently  be  described  (see  pp.  51  -52  and  Plate  III,  Fig;  B). 
They  are  also  found  in  association  with  some  of  the  old  beach  ridges 
of  Lake  Chicago,  notably  near  the  "Glenwood"  beaches  west  of  Grosse 
Point  (see  Plate  VI  and  p.  57). 

THE  SHORE  CYCLE. 

Assuming  all  that  has  been  said  regarding  the  work  of  shore  pro- 
cesses under  different  conditions  and  during  successive  stages  of  con- 
tinuous activity,  one  may  best  appreciate  the  shore  lines  to  be  studied 
if  the  changes  in  their  form  are  stated  in  terms  of  an  imaginary  "cycle" 
of  shore  action,  such  as  might  express  the  history  of  any  shore,  initially 
irregular,  which  is  acted  upon  by  the  waves  for  an  unlimited  period  of 
time.  It  may  be  said  at  the  outset  that  few  shore  lines,  if  any,  live  to 
see  the  cycle  completed,  for  the  relation  of  land  to  sea  or  level  of  the 
lake  is  never  constant  for  so  long  a  time. 

The  shore  cycle  begins  when  the  body  of  water  comes  into  a  new 
position  with  respect  to  the  land.  This  may  be  brought  about  by  a 
rising  of  the  land  (or  a  lowering  of  the  waters,  the  movement  being 
a  relative  one,  with  the  same  result  in  either  case)  such  as  is  now  in 
progress  about  Hudson's  Bay  and  in  many  other  parts  of  the  world. 


46  THE    EVANSTON-WAUKEGAN    REGION.  I  bull.  7 

The  resulting  shore  line  is  known  as  a  "shoreline  of  elevation,"  and  is 
characterized  by  long  gentle  curves,  because  it  is  determined  by  the 
smooth  floor  of  the  formerly  submerged  area.  The  coast  of  New  Jer- 
sey, briefly  described  on  pages  37-38,  may  be  taken  as  a  type. 

The  new  shore  line  may  be  formed,  on  the  other  hand,  by  a  sinking 
of  the  land  with  respect  to  the  sea.  In  this  case  the  waters  encroach 
on  the  coast  and  the  rough  stream-carved  topography  is  partly  sub- 
merged, producing  an  irregular  "shoreline  of  depression,"  of  which 
the  Chesapeake  Bay  region  is  a  conspicuous  example. 

In  the  case  of  Lake  Michigan,  the  shore  cycle  began  when  the  great 
ice-sheet  melted  off  from  the  region,  leaving  a  lake  surrounded  by 
irregular  glacial  topography.  Its  irregular  border  was  comparable  to 
a  shore  line  of  depression  in  so  far  as  it  was  undeveloped  and  unad- 
justed to  the  shore  agent. 

At  the  outset,  the  salients  and  re-entrants  of  the  irregular  coast, 
with  their  different  exposures  to  wave  action,  experience  unlike  alter- 
ation. On  the  steeply  sloping  exposed  headlands,  the  waves  cut  back 
cliffs  and  terraces,  while  the  shore  currents  shift  much  debris  along 
to  the  nearby  re-entrants.  In  the  more  gently  sloping  and  less  ex- 
posed bays,  the  waves  steepen  the  slope  by  casting  up  beaches  or  bar- 
riers, while  the  material  swept  in  from  the  headlands  considerably 
augments  the  load  and  the  tendency  to  deposition.  In  the  less  pro- 
nounced bays,  pocket  beaches  may  result,  while  the  sharper  re-entrants 
v  II  gradually  be  cut  off  by  spits,  bars  and  hooks.  So  long  as  the 
cliff ed  headlands  continue  to  project  from  the  shore  and  to  supply 
beach  material,  the  re-entrants  will  continue  to  fill  up  and  build  out- 
ward. Thus  with  receding  head-lands  and  advancing  bay  shores  there 
is  a  two-fold  tendency  to  straighten  the  shore  from  one  of  irregular 
outline  to  one  of  gentle  curves.  In  the  development  of  these  curves, 
the  waves  and  currents  will  be  guided  chiefly  by  the  initial  contour  of 
the  coast  and  the  variability  of  its  profile,  as  well  as  by  the  dominant 
winds.  The  higher  headlands  will  usually  recede  much  less  rapidly 
than  the  lower ;  the  broader  and  deeper  re-entrants  will  usually  be  the 
last  to  be  closed  by  bars ;  the  smaller  headlands  and  re-entrants  are  the 
first  to  be  replaced  by  the  curve  of  the  mature  shore,  but  gradually 
the  shore  line  becomes  an  organized  whole,  in  which  all  parts  show 
well  balanced  adjustment  to  the  forces  at  work,  and  straight  lines  and 
gentle  curves  are  the  rule.  With  continued  progress  of  the  shore 
cycle,  a  mature  shore  may  be  imagined  slowly  to  retreat  as  the  material 
along  its  border  is  lost  by  attrition,  scattering,  and  dune  action.  The 
barriers  and  bars  beaten  inland  are  succeeded  by  cliffs,  so  that  the 
entire  straightened  shore  consists  of  wave-cut  bluffs. 

The  same  progression  of  changes  in  shore  line  topography  can  be 
traced  in  a  shoreline  of  elevation,  like  that  of  New  Jersey,  the  chief 
difference  being  that  the  elevated  shore  line  begins  with  a  straightness 
comparable  to  the  sub-mature  or  mature  stage  of  a  shore  line  of  de- 
pression. 

The  great  barrier  ridges  and  brooks  of  the  extinct  Lake  Chicago 
(the  ancestor  of  Lake  Michigan)  mark  a  considerable  progress  of  the 
shore  cycle;  for  by  them  the  initially  irregular  shore  line  was  greatly 


goldthwait.I  THE    PRESENT    SHORE    LINE.  47 

straightened.  In  the  first,  highest  stage  (called  the  "Glenwood") 
as  shown  on  the  map  (Plate  VI).  Skokie  Bay  was  nearly  shut  off 
from  the  main  lake  by  the  growth  of  a  great  hooked  bar  from  Grosse 
Point  village  southward  to  Morton  Grove.  Before  the  shore  line  of 
this  Glenwood  stage  had  become  thoroughly  mature,  however,  the 
lake  fell  twenty  feet  to  the  level  of  the  second  or  Calumet  stage,  and 
a  new  cycle  was  begun.  By  the  drawing  down  of  the  waters  across 
the  smoothed  Glenwood  lake  floor  to  the  lower  level,  a  "shore  line 
of  elevation"  was  produced,  the  straightness  of  the  final  Glenwood 
beach  being  in  part  inherited  by  its  successor.  Thus  after  each  fall 
of  lake  level  the  process  of  straightening  of  the  shore  line  was  re- 
sumed, and  each  shore  line  of  elevation  was  more  nearly  mature  than 
its  predecessor. 

In  a  general  way,  the  present  cliffs  of  the  north  shore  express  the 
continually  renewed  progress  of  the  shore  cycle,  in  successive  steps, 
to  a  stage  somewhat  beyond  maturity.  But  in  reality  the  cycle  has 
been  interrupted  in  other  ways  than  by  repeated  lowerings  of  lake 
level.  As  will  be  told  further  on,  there  was  a  stage  in  the  latter 
part  of  the  lake  history  when  the  level  of  the  waters  was  much  lower 
than  now,  and  this  was  succeeded  by  a  rising  of  the  lake  upon  its 
shores  to  a  height  of  about  15  feet  above  the  present  level. 

During  this  period  of  rising  waters  came  the  greatest  advance  in 
cliff  development.  The  constant  deepening  of  the  water  favored  shore 
erosion,  and  the  lake  rapidly  advanced  into  the  land,  cutting  back  a 
long  line  of  cliffs,  which  are  still  well  preserved  north  of  Waukegan. 
Since  this  time  the  lowering  of  lake  level  has  been  resumed,  and  the 
attendant  shallowing  of  the  water  on  the  shore  has  been  unfavorable 
to  the  maintenance  of  the  cliffs.  North  of  Waukegan  a  broad  sand 
terrace  has  been  built  out,  but  south  of  Waukegan  the  lake  has 
succeeded  better  in  trimming  back  the  shore  and  the  cliffs  have  not 
only  been  maintained  but  constantly  freshened  by  encroachment. 

Inasmuch  as  erosion  by  stream  action  is  normally  going  on  all  the 
while  that  the  shore  cycle  is  progression  there  will  always  be  gaps  in 
the  cliffs  where  a  stream  valley  issues  on  the  shore ;  and  there  a  bar 
will  be  maintained  by  the  shore  drift.  An  exception  to  this  rule  of  in- 
teraction of  the  shore  cycle  and  the  river  cycle  is  found  on  the  coast 
of  Normandy,  where  the  recession  of  the  cliffs  is  so  fast  that  streams 
by  erosion  can  not  at  their  mouths  come  to  sea  level,  but  are  left  well 
up  or  "hanging"  on  the  face  of  the  cliffs.  It  is  rare  that  the  shore 
cycle  proceeds  so  much  more  rapidly  than  the  river  cycle.  All  the 
streams  entering  Lake  Michigan  within  our  area  have  lowered  their 
valleys  as  fast  as  the  shore  bluffs  have  receded. 

THE  NORTH  SHORE. 

General  Aspects — The  present  shore  line  of  this  region  may,  for  con- 
venience, be  divided  into  three  parts  according  to  its  position  with  ref- 
erence to  the  old  shore  lines  of  the  lake ;  ( i )  the  section  from  Rogers' 
Park  to  Winnetka ;  (2)  that  from  Winnetka  to  Waukegan  ;  (3)  and 
that  from  Waukegan  to  the  State  line.  Along  the  second  or  middle 
stretch  of  coast  line,  the  lake  has  cut  back  beyond  its  earlier  shores. 


48  THE   EVANSTON-WAUKEGAN    REGION.  [bull. 

North  and  south  of  it  the  ancient  beach  ridges,  terraces  and  dunes  lie 
inland  from  the  present  lake,  but  are  steadily  being  approached  and  de- 
stroyed by  the  waves.  Along  the  whole  coast,  except  possibly  for  a  few 
miles  north  of  Waukegan,  the  present  shore  line  is  being  cut  back,  and 
in  most  places  so  rapidly  as  to  call  for  vigorous  measures  for  pro- 
tection of  property  by  break-waters,  piers,etc.  Data  collected  before 
1870,  by  Dr.  Edmund  Andrews,  include  a  record  of  the  erosion  at  nine 
points  along  the  shore  within  our  area: 

At  Evanston  the  erosion  was  16.95  feet  a  year;  at  the  old  pier,  two  miles 
farther  north,  0.00  feet  a  year;   at  the  State  line,  16.50  feet  a  year. 
Winnetka,  4.05   feet  a  year;    one  mile  farther  north,   6.05  feet  a  year;   at 
Lake  Forest,  1.65  feet  a  year;    at  Waukegan,  0.00  feet  a  year;   two  miles 
farther  north,  0.00  feet  a  year;  at  the  State  line,  16.50  feet  a  year. 

Since  that  time  the  building  of  piers  along  the  whole  shore  as  far 
north  as  Waukegan  has  greatly  retarded,  though  it  has  not  stopped 
the  recession  of  the  shore.  From  Evanston  to  Waukegan  there  is  a 
continuous  line  of  clay  bluffs.  South  of  Evanston  and  north  of  Wau- 
kegan, where  the  low  sand  terrace  of  the  former  lake  shore  remains, 
the  present  beach  is  low,  and  the  indications  of  its  recession  are  less 
conspicuous.  South  of  Hyde  Park,  Illinois,  and  in  Indiana,  the  shore 
is  being  built  out  by  an  excessive  supply  of  shore  drift. 

Lake  Survey  chart  No.  4  (Lake  Michigan)  shows  that  the  lake 
floor  within  the  five  fathom  line,  usually  half  a  mile  to  a  mile  off  shore, 
is  either  sandy  or  stony,  sand  being  more  common  between  the  State 
line  and  Lake  Bluff,  and  a  stony  bottom  more  common  farther  south 
as  far  as  Rogers'  Park.  At  one  place  only  do  soundings  reveal  a  rock 
bottom — a  mile  off  Grosse  Point,  north  of  Evanston,  where  a  pro- 
tective ledge,  in  four  to  five  fathoms  of  water,  and  within  a  mile  of 
shore,  seems  to  determine  the  most  prominent  salient  of  the  shore  line. 
Beyond  the  five-fathom  line,  the  lake  shore  is  commonly  of  clay  in 
the  southern  part  of  the  area  and  of  sand  in  the  northern  part. 

The  Ten-Fathom  Terrace — The'  slope  of  the  lake  floor  between 
Rogers'  Park  and  Waukegan  is  moderately  uniform,  though  somewhat 
steeper  outside  the  ten-fathom  line  than  within  it.  Off  Waukegan 
this  change  of  slope  begins  to  be  more  pronounced,  and  a  few  miles 
farther  north,  off  Zion  City,  it  becomes  so  abrupt  as  to  mark  a  distinct 
terrace,  whose  outer  border  descends  rapidly  from  the  ten-fathom 
line,  while  within  that  line  the  terrace  rises  gently  up  to  the  shore  line, 
with  a  breadth  of  about  two  miles. 

In  his  early  paper,  of  1870,*  Dr.  Andrews  called  particular  attention 
to  submerged  terraces  shown  by  soundings  about  the  borders  of  Lake 
Superior,  Michigan  and  Huron.  These  were  said  to  extend  out  to  a 
depth  of  ten  fathoms.  He  considered  the  terrace  to  be  the  "terrace 
of  erosion"  formed  during  the  advance  of  the  present  lake  into  the 
land,  it  being  remarked  that  "the  waves  of  our  great  lakes  ceased  to 
have  any  erosive  power  upon  the  bottom  at  the  depth  of  about  60 
feet;  hence,  when  the  shores  are  worn  back  there  is  left  under  water 
a  sort  of  shelf  or  terrace,  the  surface  of  which  slopes  gently  outward 


*  '  'The  North  American  lakes  considered  as  chronometers  of  post-glacial  time."  Chi.  Acad, 
Sci..  Trans..  Vol.  II,  pp.  1-23. 


gcldthwait.]  THE   PRESENT   SHORE   LINE.  49 

to  the  depth  of  about  60  feet.  ******  Where  the  shores 
are  of  drift  clay  the  terrace  generally  has  a  breadth  of  from  two  to 
six  miles,  and  occasionally  more.  But  where  it  is  of  rock  the  width 
is  much  less.  On  some  of  the  hard  rocks  of  Lake  Superior  the  terrace 
is  scarcely  200  feet  wide.  Softer  rocks  frequently  show  a  breadth  of 
1,500  feet.  It  is  a  curious  and  unexpected  fact  that  the  depth  of  the 
erosion  is  much  less  affected  than  the  breadth  of  it  by  the  hardness 
of  the  material.  Even  rock  shores  often  show  the  edge  of  the  terrace 
to  be  60  feet  down." 

Andrews'  explanation  of  the  terrace  finds  another  contradiction  in 
his  statement  that  "the  waves  cease  to  have  power  to  move  sand  at 
the  depth  of  twenty-four  to  thirty-six  feet.  *  *  *  Beyond  thirty- 
six  feet  depth  the  bottom  [of  the  southern  part  of  Lake  Michigan]  is 
always  of  a  smooth  impalpable  clay." 

When  it  is  realized  that  a  considerable  part  of  the  material  in  the 
receding  cliffs  of  bowder  clay  is  pebbles  and  sand,  it  is  hard  to  see 
how  a  terrace  could  be  cut  in  this  material  to  a  depth  of  60  feet  by 
waves  which  fail  to  move  sand  in  water  deeper  than  36  feet.  More- 
over, we  might  well  expect  to  find  the  terrace  strongly  developed  off- 
shore from  the  present  clay  bluffs  of  the  Evanston-Waukegan  district 
if  anywhere ;  whereas  there  is  only  a  long  or  rather  gradual  slope. 

All  these  inconsistencies  suggest  that  the  terrace  may  be  better 
explained  in  some  other  way  than  by  the  activity  of  Lake  Michigan  at 
its  present  level.  It  will  be  stated  in  succeeding  pages  that  during  the 
latter  part  of  the  early  stages  of  the  lake,  the  waters  in  the  Michigan, 
Superior  and  Huron  basins  were  all  drawn  down,  at  least  50  or  75 
feet  below  their  present  level,  by  the  opening  of  a  new 
and  lower  outlet  beneath  the  retreating  ice  sheet  near  North 
Bay,  Ontario.  (See  Fig.  35.)  The  borders  of  the  lake 
basin  were  then  laid  bare  even  more  extensively  than  now. 
By  a  differential  uplift  of  the  northeastern  part  of  the  Great  Lake 
region,  which  did  not  directly  affect  the  southern  part,  this  North  Bay 
outlet  was  raised  higher  and  higher,  while  the  lakes  everywhere  in 
the  southern  parts  of  the  basins  responded  by  rising  upon  their  shores, 
submerging  them  to  a  greater  and  greater  extent,  until  they  finally 
overflowed  at  Port  Huron  (the  southern  end  of  Lake  Huron),  and 
further  drowning  of  shores  was  rendered  impossible  by  the  southern 
outlet.  It  seems  probable  that  this  ten-fathom  terrace  marks  the 
erosion  of  the  lake  border,  while  the  waters  were  rising  from  the  low 
North  Bay  plane,  to  essentially  their  present  level, — a  time  peculiarly 
favorable  to  the  cutting  back  of  a  long  line  of  cliffs  and  a  broad  ter- 
race ;  for  constant  deepening  of  the  water  means  constant  steepening 
of  the  submerged  slope  and  increase  in  the  capacity  of  the  waves  and 
currents  to  erode  and  transport  material. 

So  as  the  waters  rose  and  the  lake  cliff  was  cut  back,  a  broad, 
gently  sloping  terrace  of  erosion  might  be  worked  out,  the  outer  border 
of  which  would  be  much  too  deep  for  the  present  waves  and  currents 
to  erode,  but  at  the  depth  appropriate  to  a  terrace  cut  during  the  North 
Bay  stage.  According  to  this  explanation  we  would  be  led  to  suppose 
that  the  North  Bay  plane  of  the  lake  was  about  60  feet  lower  than  the 

-4G. 


50  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 


Fig.  29.  Diagram  showing  how  a  deeply  submerged  terrace  may  have  been  developed  by 
cliff  recession  during  a  rising  of  the  water  level  from  the  low  water  stage  to  the  "Nipissing" 
stage.  (a  b  c)  cliff  and  terrace  cut  during  low  water  stage;  (d  e  c)  cliff  and  terrace  after  the 
rise  and  encroachment  of  waters. 

present.  It  may  be  said,  however,  that  detailed  study  of  the  take 
charts  prepared  since  Dr.  Andrews'  time  shows  that  if  a  ten-fathom 
terrace  does  exist  over  a  wide  area  it  is  often  discontinuous  and  not  of 
uniform  height.    Not  too  much  emphasis  should  be  placed  upon  it* 

THE  COASTAL  TOPOGRAPHY. 

Rogers  Park  to  Winnetka. — Near  Rogers  Park,  the  beach  lies  on 
the  outer  side  of  a  broad  terrace  of  sand  ridges,  beaches,  and  dunes 
which  were  built  while  the  lake  was  falling  from  an  old  level  to  its 
present  mark.  The  crest  of  the  present  beach  rises  3  or  4  feet  above 
the  lake,  and  is  usually  well  covered  with  "shingle,"  i.  e.,  well  rounded 
discoidal  pebbles,  whose  shape  bears  witness  to  a  long  journey  along 
the  shore.  The  waves  break  moderately  close  to  shore,  showing  that 
the  profile  of  equilibrium  is  fairly  well  established  by  the  beach.  The 
conditions  are  in  some  measure  artificial,  however,  for  piers  and  break- 
waters have  been  built  at  frequent  intervals  to  catch  the  shore-drift 
and  thus  to  accumulate  a  beach  deposit  more  rapidly  than  it  can  be 
worn  out  and  transported  by  the  shore  agents.  These  piers  act  sub- 
stantially like  rock  headlands,  affording  re-entrants  or  artificial  coves 
in  which  pocket  beaches  are  built  out  in  an  endeavor  to  straighten  the 
shore  line.  From  the  end  of  each  a  submerged  sand  spit  runs  south- 
ward parallel  to  the  shore,  in  the  path  of  the  deflected  shore  current 
just  as  a  drift-built  spit  tails  out  from  a  headland  across  a  bay.  It  is 
very  noticeable  that  the  beach  accumulates  more  rapidy  on  the  north 
side  of  each  pier  than  on  the  south  side,  because  the  dominant  drift  by 
both  waves  and  currents  is  toward  the  south. 

In  spite  of  the  piers  and  artificial  beaches,  the  lake  is  advancing  on 
the  land  at  a  rather  rapid  rate.  The  cutting  is  obvious 
at  several  places  in  Rogers  Park  where  streams  run  out 
to  the  lake  shore  and  the  cement  sidewalks  or  the  ma- 
cadam road  structures  end  brokenly  at  the  border  of  the  storm 
beach.  Recession  is  just  as  truly  indicated,  however,  by  the  natural 
cliffs  cut  by  the  waves  in  the  old  beaches  10  to  15  feet  high  and  in  the 


*  Mr.  Leverett  states  in  a  letter  to  the  present  writer,  May  26,  1906,  that  after  examining 
the  charts  with  this  matter  in  mind  he  finds  frequent  terrace-like  stretches  which  s  uggest  that 
a  submerged  shore  line  rises  slowly  from  twelve  fathoms  near  Chicago  to  ten  fathoms  at 
Milwaukee  and  eight  fathoms  or  less  in  the  northern  part  of  Lake  Michigan,  as  if  from  tilting, 
But  he  does  not  regard  the  evidence  as  of  much  weight. 


goldthwait.J  THE   PRESENT   SHORE   LINE.  51 

dune  ridges.  These  dunes  are  forested,  and  have  been  established  in 
position  for  a  very  long  time,  but  are  now  being  slowly  destroyed  as 
the  waves  cut  inland.  The  recession  of  the  shore  is  accomplished,  of 
course,  only  during  heavy  storms  when  the  waves  rise  across  the 
beach  and  attack  the  sand  deposits  along  its  inner  border.  After  such 
a  storm,  when  the  water  has  subsided  to  a  lower  position  on  the  beach 
slope,  the  waves  build  up  a  secondary  beach  profile,  relatively  low  and 
weak  in  expression,  at  the  water's  edge. 

Near  the  southeast  corner  of  Calvary  cemetery,  in  South  Evanston, 
at  the  turn  in  Sheridan  Road,  is  a  small  belt  of  sand  dunes,  which  are 
not  "established"  like  those  of  Rogers  Park,  but  actively  moving  in- 
land. They  are  only  15  feet  high,  and  almost  bare  of  vegetation, 
clothed  with  almost  nothing  but  beach  grass.  The  dense  network  of 
rootlets  is  well  shown  on  the  eroded  outer  side  of  the  dunes.  The  con- 
trast between  the  bare  lake-ward  slopes  and  the  grass-covered  inland 
slopes  comes  out  well  as  one  looks  along  the  line  of  sand  hills.  (Plate 
III,  Fig.  B).  A  lone  tree,  withered  and  lifeless,  with  its  trunk  and 
spreading  roots  half  resurrected  from  a  cover  of  drift  sand  on  one  of 
the  dunes  tells  the  story  of  dune  migration,  like  the  church  at  Kurishe 
Nehrung,  or  the  resurrected  forests  at  Dune  Park. 

From  Calvary  northward  through  Evanston  to  the  Life  Saving  sta-, 
tion^  beakwaters,  piers  and  made  land  interfere  with  the  normal  shore 
line  topography.  On  the  campus  of  Northwestern  University,  the 
lower  of  the  old  shore  lines  run  obliquely  out  to  the  lake,  and  the 
low-cut  bluff  is  20  feet  high,  and  capped  by  the  beach  deposits  of  the 
Toleston,  or  20- foot,  stage  of  Lake  Chicago  (see  pp.  65-66).  A 
long  pier  at  the  Evanston  waterworks  has  induced  the  accumulation 
of  a  broad  protective  beach  at  the  north  end  of  the  University  campus, 
and  the  bluff  there  is  consequently  established.  At  Grosse  Point,  the 
bluff  consists  of  the  characteristic  till  or  bowlder  clay,  with  hardly  a 
foot  of  old  lake-floor  sediments  above  it.  Where  the  Calumet  beach 
ridge  is  cut  off  by  the  lake  at  Grosse  Point,  the  bluff  is  40  feet  high, 
and  shows  a  very  good  section  of  the  till  and  over-lying  beach  de- 
posits. The  cliffs  are  rapidly  receding  at  this  point,  and  new  land- 
slides are  often  seen  after  a  storm.  The  salient  Grosse  Point  seems 
to  be  due  in  part  to  the  protective  off-shore  ledges  and  in  part  to  the 
Calumet  beach  ridge. 

From  Grosse  Point  to  Winnetka  the  freshly  cut  bluffs  maintain  a 
height  of  25  to  50  feet,  running  obliquely  across  the  till  plain  which 
formed  the  floor  of  the  Wilmette  embayment,  during  the  Calumet 
stage  (see  Plate  VI). 

Winnetka  to  Waukegan. — In  the  northern  part  of  Winnetka  the 
bluff  (which  marks  the  highest  of  the  extinct  lake  stages)  is  cut  off 
by  the  present  shore,  and  farther  north,  for  about  20  miles,  the  lake  lies 
against  the  Highland  Park  morainic  ridge,  with  steep  cliffs  from  50 
to  100  feet  high.  These  cliffs  are  actively  receding,  although  in  most 
places  the  recession  is  very  considerably  retarded  by  the  protective 
piers,  which  obstruct  the  shore-drift  and  maintain  a  narrow  beach. 
The  southward  drift  of  shore  currents  is  clearly  seen  here,  as  elsewhere 
by  a  greater  accumulation  on  the  north  side  of  each  pier.  One  excep- 
tionally long  pier,  which  shows  this  well,  is  just  north  of  the  Cook 


52  THE   EVAN&TON-WAUKEGAN    REGION.  [bull,  t 

county  line  (Plate  V,  Fig.  A.)  Landslides  on  the  cliff  face,  gulliesy 
and  fans,  as  described  on  pages  33  and  34,  are  all  exhibited  here.  Lo- 
cally, however,  protection  is  so  efficient  as  to  allow  the  cliffs  to  become 
established  in  position  and  covered  with  young  vegetation. 

Across  the  mouth  of  each  large  ravine  the  waves  maintain  a  bar  of 
shingle  and  sand,  usually  a  complete  barrier  to  the  little  stream.  The 
streams  are  so  small  and  so  intermittent  in  their  activity  that  in  ordin- 
ary times  they  offer  no  resistance  to  the  obstructing  waves.  A  stag- 
nant pool  of  water  behind  the  bar  filters  slowly  through  the  gravels 
and  sand  as  fast  as  it  is  brought  down  the  ravine.  A  heavy  shingle 
bar  blocks  the  mouth  of  a  creek  at  the  Cook  county  line  (see  Plate  V, 
Fig.  B).  During  exceptionally  heavy  rains  and  spring  thaws, 
however,  the  stream  may  be  so  swollen  as  to  over-top  the  bar 
and  to  cut  a  channel  across  it  in  spite  of  the  opposed  wave  action.  The 
largest  streams,  of  course,  most  often  open  a  channel.  Pettibone 
Creek  is  one  of  these,  which  usually  carries  enough  water  to  maintain 
at  least  a  small  breach  through  the  south  end  of  its  bar  (see  Plate 
XII). 

Waukegan  to  the  State  Line. — At  Waukegan  a  coastal  terrace  makes 
its  appearance,  and,  rapidly  broadening,  runs  northward  with  a  width 
of  a  mile  or  more,  across  the  State  line.  This  is  a  fragment  of  the 
same  low  terrace  which  borders  the  shore  south  of  Evanston, — a  broad 
stretch  of  beach  sediments  corrugated  by  ridges  which  have  developed 
along  the  whole  shore  during  the  recession  and  subsidence  of  the  lake ; 
but  it  has  been  destroyed  by  cliff  recession  between  Waukegan  and 
Evanston.  At  its  southern  end,  in  the  yards  of  the  American  Steel 
and  Wire  Company,  at  Waukegan,  this  terrace  has  been  considerably 
extended  by  artificial  filling,  or  erosion  on  its  borders  would  doubtless 
be  as  apparent  as  on  the  face  of  the  clay  bluffs  immediately  to  the 
south.  North  of  the  city  there  is  reason  to  believe  that  the  shore  is 
stationary  or  even  building  out,  as  suggested  by  Dr.  Andrews'  figures. 
The  sandy  beach  is  bordered  by  active  dunes,  which  show  no  sign  of 
loss  on  the  outer  side  by  wave  erosion  nor  of  rapid  landward  migration. 
They  support  a  scant  growth  of  beach  grass,  juniper,  and  scrub  pine, 
which  only  imperfectly  prevents  the  shifting  of  the  sand.  Occasionally 
a  clump  of  juniper  acts  as  a  nucleus  for  a  growing  young  dune,  but 
more  frequently  the  relation  between  the  hills  and  the  juniper  seems 
to  be  very  irregular.  About  the  clumps  of  beach  grass  there  are  fre- 
quently circular  markings  on  the  sand  made  by  the  whisking  about 
of  the  grass  by  the  wind.  Gravel  appears  not  only  along  the  beach 
but  beneath  the  dunes  on  their  outer  side  and  about  10  feet  above  the 
lake,  marking  beach  deposits  of  an  extinct  stage.  In  the  dune  district 
between  Waukegan  and  Zion  City  it  is  not  apparent  whether  the  dunes 
are  moving  inland  or  not.  Since  the  winds,  especially  the  dry  winds, 
are  prevailngly  off-shore,  the  dunes  must  lose  much  material  by  scat- 
tering into  the  lake.  If  the  beach  were  advancing  lakeward,  the  dune 
belt  would  probably  be  broader  than  it  is,  for  it  is  only  100  yards  broad 
at  most,  and  toward  Waukegan  much  narrower.  Behind  the  dimes 
the  broad  tract  of  marsh,  interrupted  by  low  flattish  ridges  of  sand 
and  occasionally  sloughs  or  lagoons  of  stagnant  water,  reaches  inland 
to  the  sharply  'cut  bluff  of  an  extinct  14-foot  stage.     Dead  River  is 


coldthwait.]  THE   PRESENT   SHORE   LINE.  53 

one  of  the  largest  of  these  sloughs.  At  Zion  City,  Shiloh  boulevard 
leads  eastward  from  the  railroad  station  to  the  lake,  affording  a  good 
opportunity  to  study  the  corrugated  sand  and  marsh  terrace  and  the 
beach  and  low  dunes  of  the  present  shore.  Andrews'  figures  show  that 
the  beach  near  the  State  line  is  retreating  at  a  very  rapid  rate,  and  an 
inspection  of  the  terrace  ridges  and  sloughs  (as  shown  on  the  Coast 
Survey  chart)  confirms  this  fact.  The  ridges  run  obliquely  out  to  the 
lake,  where  they  are  successively  cut  off  by  the  advancing  beach. 

Mature  Condition  of  the  Shore  Line. — The  present  shore  line  is  one 
of  long  sweeping  curves,  well  established  profile  of  equilibrium,  and 
landward  encroachment,  having  all  the  characteristics  of  maturity. 
That  this  advanced  stage  is  due  not  simply  to  the  work  of  the  lake  at 
its  present  level,  but  in  a  large  measure  to  the  smooth  floor  and  even 
border  which  Lake  Michigan  inherited  from  its  ancestors,  has  already 
been  mentioned,  but  will  be  more  strongly  appreciated  when  the  history 
of  the  lakes  is  reviewed. 


54  THE   EVANSTON-WAUKEGAN    REGION.  I  bull.  7 


THE  RECORDS  OF  THE  EXTINCT  LAKES. 
by  j.  w.  goldthwait. 

Introduction. 

Lake  Michigan  is  the  lineal  descendant  of  a  series  of  extinct  lakes 
whose  history  is  recorded  in  raised  beaches  and  terraces,  abandoned 
outlets,  and  lake  floor  deposits  higher  than  the  present  lake.  The  an- 
cestral lakes  owed  their  high  level  to  the  great  ice  sheet,  which  acted 
as  a  dam  across  the  northern  side  of  the  basins,  holding  the  water  up 
to  the  level  of  the  lowest  notch  in  the  inclosing  land  basins.  The 
cutting  down  of  outlets,  the  uncovering  of  new  outlets  at  lower  levels 
as  the  ice  sheet  melted  northward,  and  differential  uplifts  or  tiltings 
of  the  land  combined  to  complicate  the  series  of  changes  in  level  and 
outline  of  the  lake  during  its  early  history. 

The  Evanston-Waukegan  district  contains  stretches  of  the  aban- 
doned lake  shores,  in  which  one  may  read  somewhat  imperfectly  the 
record  of  successive  events  of  lake  history.  Between  Winnetka  and 
Waukegan  the  old  shores  have  been  totally  destroyed  by  the  advance 
of  the  lake  upon  the  land;  but  north  and  south  of  this  section,  shore 
forms  of  considerable  variety  and  of  great  instructiveness  are  to  be 
seen  well  above  the  present  shore. 

In  the  Evanston  district,  the  old  lake  shore  is  much  smoother  than 
the  higher  upland  back  of  it,  and  forms  the  northern  corner  of  the 
cresentiform  Chicago  plain.  While  this  is  a  lake  plain  in  the  sense  that 
it  is  the  floor  of  an  extinct  lake,  the  plain  does  not  owe  its  flatness 
wholly  to  submergence.  The  greater  part  of  it  is  covered  with  bowlder 
clay,  thinly  veneered,  if  at  all,  by  lake  floor  sediments.  Had  the  orig- 
inal floor  been  as  irregular  as  the  upland  and  then  been  smoothed  off 
by  wave  action,  there  would  hardly  be  such  broad  stretches  of  the  lake 
plain  left  bare  of  lacustrine  sediment.  The  plain  seems  therefore  to 
be  a  glacier-made  till  plain,  whose  surface  was  given  a  finishing  touch 
by  the  lake  water  which  once  covered  it.  In  this  respect  it  is  to  be 
contrasted  with  the  broad,  flat  plains  of  the  Red  River  valley  in  Dakota 
and  in  Minnesota,  which  was  once  beneath  a  similar  ice-front  lake, 
but  is  flat  because  of  the  accumulation  of  fine  sediment  to  a  depth  of 
40  or  50  feet  on  the  lake  floor. 

In  the  Waukegan  district,  the  area  once  covered  by  the  lake  is  by 
no  means  a  plain.  It  includes  not  only  a  broad  flat  terrace  along  the 
present  lake  shore,  but  a  steep,  high  bluff,  and  a  sloping  upland  with 
several  parallel  beach  ridges. 


GOLDTHWAIT.J 


RECORDS   OF    EXTINCT    LAKES. 


55 


It  is  the  purpose  of  the  present  chapter  to  point  out  and  explain 
these  records  of  the  former  higher  levels  of  the  lake.  The  history  of 
Lake  Michigan  is  closely  connected  with  the  history  of  the  other  Great 
Lakes.  This  history  has  been  worked  out  chiefly  by  Mr.  F.  B.  Taylor, 
Mr.  Frank  Leverett,  and  Dr.  W.  C.  Alden,  of  the  United  States  Geo- 
logical Survey.* 

LAKE  CHICAGO. 

Glenwood  Stage. — At  the  time  of  its  last  great  advance,  the  North 
American  ice  sheet  reached  southward  as  far  as  the  lobate  border 
indicated  in  Fig.  30.  As  its  front  withdrew  by  melting  from  the  term- 
inal moraine,  and  began  to  uncover  the  south  end  of  the  Lake  Michigan 
basin,  a  body  of  water  appeared  between  the  ice  front  and  the  inclosing 
moraine, — a  lake  which  has  been  appropriately  named  "Lake  Chicago." 


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Fig.  30.    Map  showing  the  ice  sheet  of  the  late  Wisconsin  stage,  at  the  time  of  its 

greatest  extent. 

Its  outlet  was  through  the  lowset  notch  or  "col"  in  the  morainic 
divide  near  Chicago,  along  the  line  of  the  present  drainage  canal  into 
the  Desplaines  and  Illinois  rivers. 

When  the  lake  first  formed  along  the  margin  of  the  Michigan  ice  lobe, 
the  outlet  col  seems  to  have  been  high  enough  to  hold  the  waters  up  to 
about  60  feet  above  the  present  lake  level ;  but,  by  rapid  cutting,  it 


*  For  the  correlation  of  the  lower  stages  of  Lake  Chicago  with  Lake  Algonquin  and  the 
.Nipissing  great  lakes,  the  present  writer  accepts  all  due  responsibility.  This  part  of  the  lake 
history  must  not  be  considered  as  completely  demonstrated. 


56 


THE   EVANSTON-WAUKEGAN    REGION. 


fBULL.    7 


was  soon  lowered  a  few  feet,  becoming  stationary  at  about  55  feet 
above  Lake  Michigan.  Possibly  the  halt  at  the  55-foot,  or  Glenwood, 
level  was  determined  by  the  discovery  of  a  sill  of  bed  rock  beneath  the 
loose  drift  of  the  outlet  valley.* 


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Fig.  31.    Map  showing'  the  ice  front  lakes  and  the  ice  sheet  at  the  time  of  the  re-advance  to  the 
Port  Huron-Manistee  moraine.    ( Leverett  and  Taylor. ) 

At  one  time  before  the  close  of  the  Glenwood  stage,  the  ice  seems  to 
have  halted  in  its  retreat  and  to  have  even  re-advanced  to  the  vicinity 
of  Milwaukee,  over-riding  the  Glenwood  beach  deposits  there,  and 
burying  them  beneath  a  thick  deposit  of  ice-laid  and  water-laid  red 
clay.f 

Glenwood  Shores  in  the  Evanston  District — In  the  northern  part  of 
Winnetka,  a  short  distance  south  of  the  pumping  station,  the  cliff  and 
terrace  of  the  Glenwood  stage  appear  half  way  up  the  lake  cliff,  and 
extend  inland  with  pronounced  form  for  three-quarters  of  a  mile.  The 
terrace  is  about  55  feet  above  Lake  Michigan,  and  is  composed  of 
stratified  sand  and  gravel ;  and  behind  it  the  bluff  rises  to  a  height  of  20 


*  Investigations  by  the  writer  in  the  Chicago  outlet,  since  this  report  was  written,  make  it 
probable  that  the  level  of  Lake  Chicago  in  the  Glenwood  stage  was  controlled  not  by  a  sill  of 
rock,  but  rather  by  the  surface  of  a  gravel  deposit  (a  "valley  train")  which  occupied  the  valley 
below  Lemont,  when  first  the  ice  withdrew  from  the  district.  It  may  have  taken  the  outlet 
river  a  long  time  to  sink  its  channel  through  this  gravel  deposit,  for  it  reached  15  miles  or 
more  down  the  valley. 

t  These  are  described  by  Alden  in  the  Milwaukee  folio,  U.  S.  Geol.  Surv.  That  the  lake 
was  still  at  the  Glenwood  level  after  this  advance  seems  to  be  shown  by  the  occurrence  of  beach 
ridges  at  the  Glenwood  level,  and  superposed  upon  the  red  clay  in  Sheboygan  county,  Wiscon- 
sin, 35  miles  north  of  Milwaukee. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.  6. 


gcldthwait.]  RECORDS    OF    EXTINCT    LAKES.  57 

to  30  feet,  with  a  very  steep  slope,  affording  a  fine  outlook  for  residences 
facing  this  lake.  A  short  distance  out  from  the  base  of  the  bluff  is  a  low 
sand  ridge,  which  seems  either  to  be  an  off-shore  reef,  or  a  beach 
thrown  up  when  the  lake  fell  slightly  from  the  level  at  which  it  had  cut 
the  bluff.  A  second  sand  ridge  lies  about  a  block  east  of  the  first,  run- 
ning out  to  the  brink  of  the  lake  cliff,  as  shown  on  the  map  (Plate  VI). 

The  old  cliff  runs  southward  on  the  west  side  of  Maple  street,  becom- 
ing less  distinct  as  it  approaches  the  railroad,  where  artificial  grading 
has  destroyed  its  true  form.  On  the  west  side  of  the  railroad,  south  of 
Cherry  street,  it  appears  indistinctly.  Close  to  the  east  side  of  the 
Grosse  Point  road  is  a  belt  of  gravel  behind  which  the  rolling  upland 
of  the  Highland  Park  ground  moraine  ridge,  which  here  tails  out,  is 
covered  with  a  sheet  of  wind-blown  sand,  two  to  eight  feet  thick.  Be- 
yond the  end  of  the  moraine  west  of  Kenilworth,  the  beach 
assumes  the  form  of  a  distinct  ridge,  followed  by  the  road  to  Grosse 
Point.  A  half  mile  north  of  Grosse  Point  it  sends  out  its  first  hook  to 
the  southwest,  a  narrow  ridge  of  gravel  three-quarters  of  a  mile  long. 
In  the  southern  part  of  the  village  several  smaller  hooks  curve  sharply 
around  to  the  west,  the  outermost  forming  a  quarter  circle,  followed 
by  a  curving  road  and  connecting  with  the  most  northerly  hook  at  the 
road  corner  northwest  of  the  village.  This  outer  hook  is  much  broader 
than  the  others  and  is  made  irregular  by  a  line  of  sand  dunes,  which 
are  25  feet  high,  but  greatly  subdued  by  plowing  and  rain-wash.  A 
branch  ridge  runs  nearly  straight  west  from  this  for  over  half  a  mile. 
The  largest  hook  of  all,  however,  runs  west-southwest  from  Grosse 
Point,  and  is  followed  by  the  Glen  View  road.  This  is  a  mile  and  a  half 
long,  and  banked  up  with  a  line  of  subdued  dunes. 

About  a  mile  south  of  Grosse  Point  the  main  or  outer  beach  ridge 
divides,  the  inner  ridge  taking  a  course  a  few  hundred  feet  west  of  the 
ridge  road  which  follows  the  outer  one.  Half  a  mile  farther  on,  the 
outer  forks  again,  so  that  there  are  three  distinct  ridges,  all  parallel  and 
all  of  approximately  the  same  height.  The  outer  one  is  bordered  by  a 
terrace  which  seems  to  be  the  shore  line  of  the  next  lower  of  the  stages 
of  Lake  Chicago.  It  is  followed  for  a  mile  or  two  by  a  branch  of  the 
ridge  road,  and  gradually  spreads  and  flattens  out  at  Niles  Center. 
The  middle  of  the  ridge  determines  the  course  of  the  main  road  nearh 
as  far  as  Niles  Center,  flattening,  like  the  first,  into  a  low  sand  deposit. 
The  inner  ridge,  which  is  the  best  developed  of  all  and  a  few  feet  higher, 
sends  off  about  twelve  hooks  on  its  west  side,  and  finally  terminates  east 
of  Morton  Grove,  in  a  spreading  gravel  deposit. 

West  of  the  Chicago  river  and  southwest  of  Morton  Grove,  the  road 
to  Niles  and  Norwood  Park  follows  a  beach  ridge  which  marks  the  con- 
tinuation of  the  Glenwood  shore.  In  section  19  (Niles),  the  ridge  shows 
only  imperfectly  the  effects  of  shore  action,  being  covered  with  only  a 
thin  deposit  of  gravel  and  sand ;  but  approaching  Niles  it  becomes  a 
very  marked  ridge,  with  characteristic  sigmoid  profile  and  gravelly 
structure.     Through  the  village  of  Edison  the   shore  line  is  a  little 


58  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  1 

obscure,  forming  a  gravel  slope  against  a  moderately  steep  till  bluff ; 
but  at  Norwood  Park  (just  south  of  the  map,  plate  VI),  it  again  be- 
comes a  strong-feathered  ridge,  whose  crest,  by  railroad  levels,  is  59 
feet  above  Lake  Michigan. 

The  form  of  the  complex  set  of  hooked  bars  and  their  relation  to  the 
cut  bluff  and  gravel  beach  at  Winnetka.  indicate  that  thev  were  built 
by  strong  southward  shore  currents  which  swept  around  the  end  of  the 
eastern  moraine  ridge  and  across  the  Skokie  marsh,  which  was  then 
a  bay  (Plate  VI).  North  of  Grosse  Point  the  water  was  too  shallow 
to  permit  the  formation  of  any  considerable  hooks,  the  shore  currents 
running  straight  southward  ;  but  south  of  that  place,  where  the  currents 
ran  out  into  deeper  water,  they  were  subject  to  frequent  deflection,  and 
well  marked  hooks  were  built  one  after  another  as  the  bar  grew,  like  the 
hooks  on  Rockaway  Beach,  Long  Island  (Fig.  2j).  So  far  was  the 
hooked  bar  extended,  that  it  nearly  shut  in  the  Skokie  embayment, 
leaving  a  gap  at  Morton  Grove  only  a  mile  wide.  The  building  of  the 
middle  and  outer  ridges  may  have  been  initiated  by  a  very  slight  fall 
of  lake  level,  toward  the  close  of  the  Glenwood  stage.  .  The  northward 
weakening  of  the  Glenwood  beach  from  Niles  toward  Glenview,  shows 
the  effect  of  the  Grosse  Point  bar  in  protecting  the  shores  of  the  Skokie 
re-entrant. 

There  was  doubtless  an  embayment  also  in  Glenwood  time  in  the 
Desplames  valley,  running  northward  at  least  as  far  as  Desplaines,  but 
no  distinct  shore  topography  was  developed  in  so  shallow  and  so  pro- 
tected a  re-entrant.  It  was  shut  off  from  the  open  lake  by  a  great 
hooked  split,  at  Oak  Park.* 

Glenwood  Beaches  in  the  Waukegan  District — In  the  city  of  Wau- 
kegan  the  Glenwood  beach  ridge  may  be  found  just  east  of  Genesee 
street,  running  northward  on  the  west  side  of  Sheridan  road  not  far 
back  from  the  top  of  a  steep  bluff  that  marks  a  much  lower  stage 
(Fig.  32).  Although  usually  much  obscured  by  grading,  the  beach 
ridge  is  in  some  places  quite  distinct  and  has  an  altitude  of  50  to  55  feet 
above  the  lake.  In  the  southern  part  of  the  town  it  seems  to  have  been 
cut  off  by  the  advance  of  the  lake  on  the  land  at  a  later  time.  When 
followed  northward  it  is  seen  to  cross  the  Kenosha  highway  in  section 
16,  and  to  follow  close  to  the  brink  of  the  Toleston  bluff  where  the 
road  runs  eastward  (between  sections  16  and  9)  to  the  lake.  The 
Glenwood  ridee  is  closelv  associated  with  rolling  morainic  mounds, 
which  in  places  are  quite  sandy  and  may  in  part  be  covered  with  dune 
sand.  In  section  o  (Waukegan)  the  55-foot  ridge  is  broken  in  several 
places. by  transverse  streams.  Behind  the  bar  a  small  creek,  following 
a  deflected  course  for  a  mile  or  more,  has  cut  a  deep,  terraced  valley. 
Curious  topography  produced  by  the  encroachments  of  the  lake  on  the 
one  hand  and  the  terracing  of  the  deflected  stream  on  the  other,  will  be 
described  in  a  later  chapter  (pages  83-84). 


*  See  Salisbury  and  Alden,  '  'The  Geography  of  Chicago  and  Its  Environs,  "  Geog.  Soc.  Chi. 
Bull.  1,  pp.  35  to  37. 


60  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

In  section  4  (Waukegan)  the  beach  ridge  continues  northward  with 
characteristic  strength,  and  thence  for  over  six  miles  is  followed  by 
Sheridan  road.  Near  Beach  station  it  has  three  closely  set  crests.  At 
Zion  City  it  is  double,  the  two  ridges  having  the  same  height,  53  feet 
above  the  lake,  and  crossing  Shiloh  boulevard  near  Dowie's  residence. 
In  places  it  is  raised  a  few  feet  by  blown  sand.  Near  Withrop  Harbor 
it  is  again  double  and  not  so  well  defined.  Behind  it,  on  the  outer  slope 
of  the  till  ridge,  a  low  cliff  has  developed.  The  beach  ridge  crosses  the 
State  line  with  a  crest  which  rises  and  falls  several  feet  because  of 
dune  action. 

West  of  this  50  to  55-foot  Glenwood  beach  ridge  is  another  long 
ridge,  from  5  to  15  feet  higher,  usually  much  broader,  and  commonly 
so  till-like  in  structure  as  to  suggest  an  ice-front  deposit  rather  than 
a  beach  ridge.  Locally,  however,  (as  at  the  gravel  pit  at  the  southeast 
corner  of  section  9,  near  Winthrop  Harbor),  it  is  seen  to  be  built  of 
well  stratified  gravels.  As  is  shown  by  the  map,  this  till  and  gravel 
ridge  can  be  followed  continuously  from  the  State  line  nearly  to 
Waukegan,  where  it  blends  with  the  rolling  morainic  topographv. 

This  outermost  ridge,  60  to  70  feet  above  Lake  Michigan,  might 
be  regarded  as  a  deposit  formed  near  and  in  part  against  the  ice  front 
when  Lake  Chicago  was  first  opening  and  before  the  erosion  of  the 
Chicago  outlet  had  established  a  50  to  55-foot  mark.  The  lake  at  that 
time  was  probably  only  a  narrow  belt  of  water  against  the  ice  (some- 
what broader,  however,  north  of  Zion  City),  and  wave  action  was  weak 
and  embarrassed  by  ice-front  accumulations. 

THE  CHANGE  FROM  THE  GLENWOOD  TO  THE  CALUMET  STAGE. 

While  the  ice  front  receded  and  Lake  Chicago  expanded  northward, 
the  erosion  of  the  outlet  floor  seems  to  have  been  suddenly  checked, 
and  to  have  ceased  temporarily ;  so  as  to  hold  the  lake  for  a  consider- 
able time  at  a  level  about  35  feet  above  the  present.  It  seems  as  if 
the  drop  from  55  to  35  feet  was  a  rather  sudden  one,  for  the  Glen- 
wood and  Calumet  beaches  are  usually  quite  distinct,  with  no  beaches 
to  mark  intermediate  stages.  Accordingly,  a  process  of  sudden  deep- 
ening of  an  outlet,  known  as  "stoping,"  has  been  suggested.  In  brief, 
it  is  as  follows  :* 

The  outlet  of  a  lake  may  flow  across  a  region  of  hori- 
zontally bedded  rocks  in  which  certain  layers  are  weak  and 
others  resistant  (see  Fig.  33,  upper  diagram).  Under  such 
conditions  rapids  or  even  falls  are  likely  to  be  developed  where 
a  river  runs  off  from  the  hard  stratum  on  to  the  weak  one.  While  in 
the  upper  portion  of  the  outlet,  the  hard  layer  suffers  very  little  erosion, 
the  rapids  farther  down  quickly  work  up  stream,  by  sapping  or  stoping. 
Thus,  while  the  lake  is  held  to  the  level  of  the  sill  at  the  head  of  the 
outlet,  the  rapids  work  up  stream  nearer  and  nearer  the  lake,  and 
finally  cut  through  the  sill  with  a  rush,  and  the  lake  level  falls  suddenly 
into  adjustment  with  the  flat  "stope."     It  is  not  even  necessary  to 


*  This  explanation  is. merely  an  abstract  of  Professor  Chamberlin's  original  presentation  of 
the  view  of  stoping,  in  Monograph  XXV,  of  the  U.  S.  Geol.  Surv.,  '  'Lake  Agassiz, "  pp.  250-251. 


GOLDTHWAIT.  j 


RECORDS   OF    EXTINCT    LAKES. 


61 


postulate  a  bed  rock  structure,  for,  if  the  outlet  is  across  a  morainic 
ridge  whose  outer  border  is  moderately  steep  and  whose  structure  is 
locally  very  resistant,  stoping  may  take  place.  Suppose,  for  instance, 
that  in  Figure  33  (lower  diagram)  an  outlet  for  the  lake  is  found 
across  the  moraine  in  a  line  of  cross-section,  and  that  at  b-c  there  is 
an  exceptionally  resistant  belt  of  drift,  more  bowldery  and  compact 
than  the  surrounding  drift.  Profiles  of  erosion  would  develop  in  suc- 
cession somewhat  as  indicated  in  the  figure,  rapids  forming  first  on  the 
outer  side  of  the  resistant  band  and  working  up  stream  until  they  cut 
through  the  obstruction,  whereat  the  weaker  material,  no  longer  pro- 
tected, would  quickly  yield  to  erosion  and  the  lake  would  fall  to  fit 
the  new  channel  floor. 


Fig.  33.  Diagrams  showing  in  profile  how  the  level  of  a  lake  may  suddenly  fall  by 
'  'stoping."  In  the  upper  figure  the  stoping  is  through  horizontal  bed  rock.  In  the  lower  one  it 
is  through  a  resistant  portion  of  the  moraine,  a,  b.  c,  d  are  successive  positions  of  the  top  of 
the  rapids  developed  by  stoping;  e  is  the  final  position  of  the  head  of  the  outlet. 

THE   CALUMET  STAGE.* 

The  lake  remained  at  the  new  level,  35  feet  above  the  present  lake, 
for  another  long  interval,  while  the  ice  withdrew  toward  the  northern 
part  of  the  Great  Lake  region.  Strong  beaches  and  terraces  were 
formed  in  the.  Chicago  district,  and  northward  at  least  as  far  as  Lud- 
ington,  Michigan,  and  Manitowoc,  Wisconsin.  How  much  farther 
north  they  extended  is  not  known.  The  Calumet  stage  seems  to  have 
closed  with  the  lowering  of  the  Chicago  outlet  of  the  lake  10  to  15. 
feet.f 

Calumet  Shores  in  the  Evanston  District. — During  the  Calumet 
stage,  nearly  the  entire  till  plain  east  of  the  Glenwood  beach  was 
submerged,  for  it  all  lies  below  the  35-foot  mark.     The  border  of  the 


*  It  has  long  been  supposed  (following  Dr.  Andrews)  that  the  Glenwood  and  Calumet  stages 
were  separated  by  a  stage  of  low  water  when  the  lake  fell  to  a  level  at  least  as  low  as  the 
present  and  probably  much  lower.  The  evidence  cited  is  a  peat  bed  which  lies  beneath  the 
Calumet  ridge  at  Grosse  Point.  But  recent  study  of  this  locality  strongly  suggests  the  '  'peat" 
is  merely  a  lacustrine  deposit,  formed  in  quiet  water  behind  the  barrier  during  the  Calumet 
stage,  and  buried  by  shoreward  advance  of  the  reef.  Other  evidences  of  a  low  lake  stage,  once 
correlated  with  the  pre-Calumet  stage,  seem  now  to  belong  to  much  later  periods,  described  on 
pages  63  and  66. 

t  Recently  evidence  has  been  found  at  Lockport  which  seems  to  indicate  that  this  second 
drop  in  level  of  Lake  Chicago  was  accomplished  by  stoping  of  the  old  outlet  through  a  sill  of 
bed  rock  at  that  place. 


62  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

lake  was  near  the  outer  Glenwood  bar.  Between  Niles  Center  and 
Grosse  Point,  it  is  marked  by  a  pretty  distinct  terrace  of  gravel,  sand, 
and  black  soil,  such  as  might  be  expected  to  form  along  the  shore  of 
an  embayment.  About  three  miles  east  of  this,  a  great  off-shore  barrier 
was  built  at  this  stage,  the  Rose  Hill  barrier,  which  is  followed  for 
six  miles  by  Ridge  avenue,  through  Evanston  and  Rogers  Park,  and 
terminates  near  Rose  Hill  cemetery.  This  barrier,  like  the  Glenwood 
bars,  was  doubtless  constructed  in  part  by  southward  shore  currents, 
which  brought  gravels  and  sand  from  the  cliffs  east  of  Winnetka.  But 
all  of  the  ridge  north  of  Grosse  Point,  and  the  associated  cliffs,  have 
been  cut  away  by  Lake  Michigan,  the  Ridge  avenue  bar  then  protected 
a  long  lagoon,  which  we  may  call  for  convenience  the  Wilmette  em- 
bayment, since  Wilmette  is  near  the  head  of  the  bay  and  on  its  floor. 
The  Ridge  is  a  conspicuous  feature,  and  is  widely  known  for  its  well- 
built^  boulevard  and  its  fine  residences.  It  rises  about  20  feet  above 
the  flat  till  plain,  with  a  steeper  slope  usually  on  the  western  side  than 
on  the  east  or  front.  While  the  whole  barrier  deposit  shows  a  width 
of  a  quarter  to  a  half  of  a  mile,  the  beach  ridge  on  its  outer  side  is 
very  narrow  (see  Plate  VI). 

At  the  termination  of  the  ridge,  near  Grosse  Point,  a  freshly  exposed 
cross-section  may  usually  be  seen  in  the  lake  cliff,  in  which  the  brown 
cross-bedded  beach  gravels  overlie  horizontally  bedded  sand  and  the 
glacial  bowlder  clay.  Close  to  the  base  of  the  stratified  portion  is  a 
band  of  peaty  clay,  very  thinly  laminated,  and  composed  in  part  of 
bits  of  wood  and  decayed  plant  stems.  This  was  thought  by  Dr. 
Andrews  to  indicate  a  condition  of  low  water  between  the  Glenwood 
and  Calumet  stages;  but  it  may  with  equal  reason  be  regarded  as  a 
layer  of  lagoon  muds  and  plant  remains  buried  by  the  on-shore  migra- 
tion of  the  barrier.  The  crest  of  the  ridge,  where  it  is  gravelly  to  the 
surface  (and  thus  evidently  an  outer  beach  ridge  unmodified  by  dunes) 
is  usually  about  38  feet  above  Lake  Michigan.  But  locally  the  beach 
ridge  is  coated  with  wind-blown  sand,  which  raises  it  several  feet 
higher. 

On  the  west  side  of  the  barrier  are  minor  beach  ridges  and  distinct 
hooks,  which  show  that  wave  and  current  action  in  the  Wilmette  em- 
bayment was  vigorous,  and  independent  of  the  waves  upon  the  lake. 
The  best  of  these  hooks  diverges  from  the  main  ridge  southwest  of 
Rogers  Park,  running  out  a  mile  into  the  open  bay,  with  a  graceful 
curve,  and  ending  near  the  center  of  section  25,  just  south 
of  the  Chicago  city  line  (Plate  VI).  On  it  can  be 
traced  a  gravelly  beach  ridge,  built  by  the  bay  waves, 
and  a  higher  dune  ridge.  Two  small  but  very  distinct 
branch  hooks,  with  crests  nearly  as  high  as  the  Ridge  avenue 
beach,  occur  in  Rogers  Park.  A  good  place  to  see  one  of  these  is  a 
field  near  the  corner  of  Lunt  avenue  and  Pine  street.  The  low  ground, 
protected  by  the  long  hook,  is  covered  with  fine  lake  sediments, — a 
stretch  of  true  "lake  plain,"  on  which  there  are  large  truck  farms. 
These  hooked  spits  indicate  clearly  that  there  was  pretty  strong  wave 
action  in  the  Wilmette  bay,  inducing  a  northward  shore  current  just 
opposite  in  direction  to  the  shore  current  on  the  outer  side  of  the  Ridge 
avenue  bar.  The  case  is  analogous  to  that  of  Sandy  Hook  and  its 
branch  spits  (described  on  page  43)  ;  and  a  comparison  of  the  two  is 


goldthwait.]  RECORDS   OF   EXTINCT   LAKES.  63 

interesting  and  instructive.  The  dominant  waves  in  the  Wilmette  bay 
came  with  a  south  or  southwest  wind,  for  they  had  the  greatest  "fetch." 
A  short  branch  spit,  which  crosses  Hill  street  just  north  of  the  Evans- 
ton  golf  links,  at  Ridge  avenue,  shows  again  the  northward  drift  of 
beach  material  on  the  bay  side  of  the  great  barrier. 

Calumet  Beach  in  the  Waukegan  District. — In  the  northern  part  of 
Waukegan,  two  miles  north  of  the  city  (in  section  9)  scraps  of  terraces 
at  altitudes  appropriate  to  the  Calumet  stage  appear  on  the  face  of  the 
Toleston  bluff;  but  some  of  these  at  least  seem  to  be  old  ravine  ter- 
races, preserved  in  a  curiously  exposed  position. 

Near  Beach  Station  (Fig.  32)  the  Calumet  ridge  ap- 
pears on  the  brink  of  the  Toleston  bluff,  and  runs  north- 
ward with  short  interruptions  to  the  State  line,  never  far 
from  the  bluff  of  the  lower  stage.  Through  Zion  City 
it  is  followed  by  Elizabeth  avenue.  Near  Winthrop  Harbor  it 
was  cut  away,  during  the  Toleston  stage,  for  half  a  mile.  Although 
usually  a  low,  faint  feature,  and  subdued  by  plowing,  it  is  broad  and 
strong  between  Zion  City  and  the  Camp  Logan  road.  Here  a  peaty 
deposit,  lying  between  the  Glenwood  and  the  Calumet  beach  ridges, 
contains  a  great  abundance  of  fresh  water  shells.* 

Since  these  shells  are  all  of  living  species  and  none  have  been  found 
either  here  or  elsewhere  within  the  stratified  deposits  of  the  Calumet 
beach,  they  seem  not  to  belong  to  Calumet  time,  but  rather  to  the 
present.  There  are  no  certain  traces  of  life  in  the  lake  during  the 
Glenwood  and  Calumet  stages. 

INTERVAL    BETWEEN    THE    CALUMET    AND    TOLESTON    STAGES. 

It  is  not  known  how  far  north  the  ice  had  receded  during  the  Calu- 
met stage  before  the  Chicago  outlet  was  lowered  and  Lake  Chicago 
fell  to  10  or  15  feet.  There  is  reason  to  believe  that  soon  after  the  fall 
occurred  the  ice  uncovered  a  still  lower  outlet  to  the  northeast  and 
for  a  time  the  lakes  experienced  a  low-water  stage. 

The  chief  evidences  of  this  low-water  stage  are,  (1)  peat  deposits 
buried  by  Toleston  gravels  in  Evanston  and  elsewhere,  and  (  2) 
drowned  valleys  on  the  east  side  of  Lake  Michigan,  described  by  Lever- 
ett  as  a  record  of  deep  channeling  in  adjustment  to  a  lake  level  at 
least  50  feet  lower  than  the  present,  a  channeling  which  took  place  after 
the  Glenwood  stage  and  before  the  Toleston. \ 


*  Identified  by  Mr.  Bryant  Walker  of,  Detroit:    Lynnaea  reflexa  (Say.),  Planorbis  trivalvis 
(Say.),  Planorbis  bicannatis  (Say.),  Planorbis  parvus  (Say.).'Physa  elliptica  (Lea.),    Pisidium 

t  It  is  perhaps  possible  that  these  valleys  were  both  deepened  and  drowned  at  a  time 
subsequent  to  a  25-foot  stage,  for  there  is  good  evidence  of  a  later  low  water  stage. 


64 


THE    EVANSTON-WAUKEGAN    KEGION. 


[bull.  7 


LAKE     ALGONQUIN,     THE     LOW-WATER     STAGE,     AND     THE     NIPISSING 

GREAT   LAKES. 

^  The  name  Toleston  has  been  given  to  a  group  of  shore  lines  in  the 
Chicago  district  which  lie  from  10  to  25  feet  above  Lake  Michigan. 
The  Toleston  beaches  fall  pretty  definitely  into  two  divisions,  a  higher 
group,  from  20  to  25  feet  above  the  lake,  and  a  lower  group,  from  12 
to  15  feet.  The  higher  area  always  marked  by  beach  ridges;  the  lower 
frequently  by  a  distinct  wave  cut  cliff. 

Recent  studies  have  strengthened  the  belief  that  the  15-foot  mem- 
ber of  the  Toleston  group  of  beaches  does  not  mark  the  shore  of  a 
local  Lake  Chicago,  but  of  two  of  its  larger  successors,  Lake  Algon- 
quin and  the  Nipissing  great  lakes.* 

While  this  is  not  yet  fully  demonstrated,  it  will  be  seen  to  explain 
certain  features  of  the  Toleston  beaches  in  the  Evanston-Wauk^egan 
district  in  a  way  which  other  interpretations  fail  to  do,  especially  the 
strong  development  of  the  lower  Toleston  bluff. 


Fig.  34.  Map  showing  the  supposed  outline  of  Lake  Algonquin  and  its  contemporaries. 
The  position  of  the  ice  border  is  hypothetical.  The  outline  of  the  lakes  is  known  chiefly 
through  the  work  of  Taylor  and  Leverett. 

Lake  Algonquin  occupied  the  whole  of  the  Michigan  and  Huron 
basins  and  part  or  all  of  the  Superior  basin.  It  came  into  the  Michi- 
gan basin  when  the  ice  had  uncovered  the  Straits  of  Mackinac  and 
Lake     Chicago     coalesced     with     its     contemporary     in     the     Huron 


*See  "Abandoned  Shore  Lines  of  Eastern  Wisconsin,  "  by  J.   W.   Goldthwait. 
and  Nat.  Hist.  Surv.,  Bull.  XVII,   1907. 


Wis.  Geol. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.  7. 


Fig.  A.    Lower  Toleston  cliff  and  beach  ridge. 




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goldthwait.  ]  RECORDS   OF    EXTINCT   LAKES.  65 

basin.  At  that  time  the  discharge  of  Lake  Algonquin  seems  to  have 
been  eastward  across  Ontario,  through  the  Trent  valley,  a  region 
which  at  that  time  stood  much  lower  than  now ;  but  it  was  later  shifted 
to  Port  Huron,  by  uplifts  of  the  more  northerly  region.  The  Chicago 
outlet  may  have  shared  to  a  slight  decree  in  draining  Lake  Algon- 
quin, but  the  outlet  at  Port  Huron  finally  obtained  the  whole  dis- 
charge by  being  cut  down  more  rapidly  than  the  outlet  at  Chicago. 
During  the  long  Algonquin  stage,  the  northern  part  of  the  great  lake 
suffered  tiltings  or  differential  warpings,  which  brought  the  shores  up 
out  of  water  and  left  them  in  deformed  attitudes,  rising  and  diverg- 
ing vertically  toward  the  north.  The  Lake  Michigan  basin  south  of 
Manistee,  however,  and  the  Huron  basin  south  of  Point  Au  Barques 
seems  to  have  been  unaffected  by  the  movements,  so  that  the  15-foot 
beach  in  that  southern  portion  of  the  Great  Lake  region  is  still  hori- 
zontal.* 

The  To  lest  on  Beaches— The  main  Toleston  beach  ridge  makes  its 
appearance  not  far  north  of  the  campus  at  Northwestern  Univer- 
sity, in  Evanston.  From  the  waterworks  southward  beyond  the  obser- 
vatory, the  inner  half  only  of  the  beach  ridge  is  preserved,  on  the  brink 
of  the  present  lake  bluff.  But  at  the  north  gate  of  the  campus,  the  com- 
plete ridge  runs  inland  from  the  lake,  beneath  Heck  Hall  and  Univer- 
sity Hall.  (See  Plate  VII,  Fig.  B.)  Thence  its  course  through  the 
city  is  on  the  east  side  of  Chicago  avenue  to  South  Evanston,  where 
it  is  followed  pretty  closely  by  Clark  street  to  the  southern  borders  of 
the  map.     (Plate  VI.) 

Its  crest  on  the  University  campus  is  24  feet  above  the  lake,  the  upper 
4  feet  being  sandy,  though  perhaps  not  from  dune  action.  A  recent 
cross-section  in  the  bluff,  where  the  ridge  runs  out  to  the  lake,  showed 
one  foot  of  peat  about  5  feet  above  the  lake,  beneath  the  Toleston 
gravels.  Below  the  peat  is  a  compact  deposit  of  very  fine  gray  sand,  of 
unknown  depth.  A  single  shell  was  found  in  the  sand  close  to  the  peaty 
layer.  A  section  studied  by  Leverett  m  1888  showed  similar  peat  layers, 
with  associated  shell-bearing  clays  nine  feet  above  the  lake.  Dr.  Oliver 
Marcy,  in  1864,  made  a  record  of  an  exceptionally  good  exposure  in  the 
cliffs,  which  were  then  unprotected  by  the  piers  and  artificial  beach. 
The  peat,  a  clay  bed  containing  molluskan  shells  of  nine  genera  (all 
existing  species)  was  found  ten  feet  above  the  lake.  Farther  down, 
on  the  contorted  glacial  clays,  was  found  a  "humus  soil,  with  stumps  and 
logs  (coniferous),"  six  inches  thick  and  buried  by  three  feet  of  gravel. 
A  cellar  excavation  on  Davis  street,  Evanston,  recently  showed  a  peat 
bed  between  the  blue  bowlder  clay  and  the  over-lying  Toleston 
gravels  and  sands.  Minute  fibrous  rootlets  could  be  seen  pene- 
trating the  till  at  the  base  of  the  peat,  indicating  that  the  deposit  is  in 


*  Leverett  and  Taylor  have  found  no  beach  extending  up  to  the  region  of  coalescence,  in 
either  of  the  basins,  above  the  Algonquin  plane.  In  eastern  Wisconsin,  likewise,  no  beaches 
above  the  Algonquin  seem  to  extend  north  of  the  Manistee  moraine. 

—5  G 


66  THE   EVANSTON-WAUKEGAN    REGION.  [bum,.  7 

situ,  presumably  a  land  surface  deposit.  If  so,  it  registers  a  stage  of 
low  water  preceding  the  Toleston.  A  marl  bed  near  the  base  of  the 
Toleston  gravels  here,  contains  an  abundance  of  shells. 

South  of  Cavalry  cemetery,  through  Rogers  Park,  the  Toleston  ridge 
is  associated  with  a  higher  ridge  of  dunes,  which  lies  between  Clark 
street  and  the  Northwestern  railroad,  and  has  an  altitude  of  25  to  30 
feet  above  the  lake.  A  measurement  in  a  borrow  pit  near  Calvary, 
where  the  gravel  ridge  is  covered  with  five  feet  of  sand,'  places  the  top- 
most gravel  layer  22  feet  above  Lake  Michigan.  This  seems,  then,  to 
be  about  the  height  of  the  outer  Toleston  beach. 

Below  this  highest  ridge  of  the  Toleston  group  are  always  several 
lower  beach  ridges.* 

In  the  Waukegan  district  no  beaches  occur  at  the  20  to  25-toot  level. 
Beaches  of  this  stage  were  destroyed  by  the  recession  of  the  bluffs 
when  the  lake  stood  about  15  feet  above  its  present  level  (lower  Toles- 
ton or  Nipissing  stage). 

Lake  Algonquin  was  extinguished  by  the  recession  of  the  ice  front, 
uncovering  a  low  pass  between  Lake  Nipissing  and  the  Mattawa 
river  (east  of  North  Bay,  Ontario.)  The  waters  fell  considerably  in 
adjustment  to  the  new  outlet  and  the  Port  Huron  pass  was  left  high  and 
dry.  It  is  not  known  just  how  far  the  lake  fell  to  the  new  outlet.  If 
the  ten-fathom  terrace  already  described  on  pages  48-50,  is  of  signifi- 
cance in  this  connection,  the  drop  as  registered  in  the  Michigan  basin 
was  about  60  feet.  But  this  terrace  is  a  questionable  one.  With  a  fall 
of  60  feet,  the  lake  would  have  assumed  some  such  outline  as  that  shown 
in  Figure  35. f 

The  low  water  stage  was  not  to  endure,  however,  for  continued 
upwarping  of  the  northern  part  of  the  lake  region  raised  the  North 
Bay  pass  up  to,  and  at  last  above,  the  level  of  the  recentlv  abandoned 
Port  Huron  pass.  Everywhere  south  of  the  rising  outlet  the  lakes 
responded  by  rising  on  their  shores  until  the  waters  overflowed  again 
at  Port  Huron.  (Fig.  36.)  This  transition  stage,  mark- 
ing the  climax  of  the  rising  of  the  lakes,  when  both  the 
Nipissing  and  the  Port  Huron  outlets  were  in  use,  has 
been  called  the  stage  of  the  Nipissing  great  lakes,  and 
its  shore  line  the  Nipissing  shore  line.  In  the  southern  part  of  the 
Michigan  and  Huron  basins  the  shore  line  of  this  stage  seems  *to  be 
10  or  15  feet  above  the  present  lakes,  and  in  a  horizontal  position ;  but 
toward  the  north  the  old  shore  line  rises  gradually  and  very  uniformly 
as  a  result  of  the  tilting.  The  shore  lines  of  the  Nipissing  stage  are 
characterized  by  an  exceptionally  strong  development  of  cut  bluffs 
and  terraces,  rather  than  by  beach  ridges.  In  this  manner  they  express 
the  vigorous  encroachment  of  a  lake  which  was  rising  upon  its  shores 
(see  Fig.  29). 

*  On  the  University  campus  the  Toleston  ridges  occur  at  heights  of  24,  23.  19,  16  and  14 
feet.  At  Chase  avenue,  Rogers  Park,  they  are  30  feet  (a  dune  covered  ridge  on  the  west  side  of 
Clark  street),  23  feet  (east  side  of  Clark  street),  23  feet,  16  feet  (one  block  east  of  Clark  street) 
and  many  others  from  10  to  15  feet  above  the  lake.  There  is  reason  for  including  those  below  16 
feet  in  the  second  or  lower  division  of  the  Toleston. 

t  Recent  studies  strongly  suggest  that  the  low-water  stage  was  very  much  lower  than  this— 
perhaps  at  about  sea  level. 


GOLDTHWAIT.] 


RECORDS    OF    EXTINCT    LAKES. 


67 


Fig 


35.    Map  showing  a  possible  outline  of  the  Great  Lakes  at  the  low  water  stage 
just  preceding  the  Nipissing  stage. 


Fig.  36.    Map  of  the  Nipissing  Grea    Lakes.    (After  Taylor.) 


68  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

At  the  close  of  the  Nipissing  stage,  uplifts  brought  the  North  Bay 
outlet  above  water,  and  the  discharge  through  the  Saint  Clair  river 
was  fully  restored.  From  that  time  to  the  present,  the  only  permanent 
changes  in  level  have  been  a  lowering  of  the  lake,  in  response  to  the 
continued  deepening  and  widening  of  the  outlet.  It  is  this  lowering, 
without  doubt,  causing  the  lake  to  slowly  withdraw  from  its  Nipissing 
shore  line,  which  resulted  in  the  accumulation  of  the  broad  sand  ter- 
race of  beach  and  dune  ridges  bordering  the  lake  in  the  Waukegan 
district,  and  near  Rogers  Park. 

Lower  Toleston  Bluff  and  Shore  Terrace  in  the  Waukegan  District. 
— The  rising  of  the  waters  from  the  low  water  stage  to  the  Nipissing 
level  was  attended  by  vigorous  cliff  cutting  in  the  Waukegan  district. 
This  is  clearly  shown  by  the  conspicuous  bluff  which  lies  just  west  of 
the  Chicago  &  Northwestern  railroad  all  the  way  between  Waukegan 
and  the  State  line.  (Plate  VII,  Fig.  A.)  In  height, 
this  bluff  varies  from  15  to  40  feet,  according  to  the 
distance  it  receded  into  the  upland.  It  is  higher  between 
Waukegan  and  Beach  Station  than  north  of  that  place.  It 
is  usually  very  steep  except  where  long  cultivation  has  favored  the 
reduction  of  its  steep  slope.  The  base  of  the  bluff,  sometimes  bordered 
by  a  cut  and  built  terrace,  is  usually  13  or  14  feet  above  Lake  Michigan ; 
but  near  Waukegan  it  seems  to  be  only  5  or  10  feet  above  the  lake, 
probably  because  it  was  trimmed  away  during  the  subsequent  fall  of 
the  waters  to  their  present  level.  In  general,  however,  the  lowering 
of  level  has  resulted  in  the  over-shallowing  of  the  shore,  and  the  con- 
struction of  a  broad  terrace  of  low  sand  ridges,  described  on  page  52. 
Between  Zion  station  and  the  lake,  24  of  these  sand  ridges  cross  Shiloh 
boulevard.  Farther  south,  the  number  becomes  much  less  until  near 
Waukegan  there  is  only  a  broad  marsh  with  sloughs  between  the  Toles- 
ton bluff  and  the  present  beach.  North  of  Zion  the  terrace  becomes 
higher  and  drier  and  more  extensively  wooded. 

EFFECTS  OF  RECENT  FLUCTUATIONS  IN   LAKE  LEVEL. 

Since  the  settlement  of  the  Great  Lake  region  the  level  of  Lake 
Michigan  and  Lake  Huron  has  fluctuated  noticeably.  Not  only  is  there 
a  regular  seasonal  fluctuation  of  about  one  and  one-half  feet  (high 
water  coming  in  June  or  July,  and  low  water  in  midwinter) ,  but  there 
are  greater  changes  through  periods  of  several  years.  In  1886  the 
lake  was  about  two  feet  higher  and  in  1896  nearly  three  feet  lower 
than  in  1906.  At  high  water  in  1838  the  lake  stood  nearly  six  feet 
higher  than  at  low  water  in  1896.  When  these  secular  changes  of  level 
are  plotted  next  to  a  rainfall  curve*  the  connection  between  periods  of 
unusual  rainfall  or  drought  and  periods  of  high  or  low  water  is  evi- 
dent. With  such  considerable  fluctuations,  known  by  actual  gauge 
measurements,  it  seems  likely  that  a  good  part  of  the  low  coast  near 
Waukegan  has  been  built  up  within  historic  times. 

*  This  has  recently  been  done  in  "Geologry  of  Huron  County,   Michgan,"  by  A.  C.  Lane, 
Geol.  Surv.  of  Mich..  Vol.  VII,  Part  2,  plate  5. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PL  8. 


Fig.  A..    Moraine  upland  descending  to  lake  shore. 


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Fig.  B.    Young  valleys.      [Courtesy  of  Wisconsin  Geol.  Nat.  Hist.  Surv.] 


atwood.]  DEVELOPMENT   OF    RAVINES.  69 


THE  DEVELOPMENT  OF  THE  RAVINES  * 
By  W.  W.  Atwood. 

Morainic  Surface — The  surface  of  the  drift,  when  exposed  by  the 
retreat  of  the  ice,  was  probably  somewhat  rougher  than  much  of  the 
upland  of  today.  The  drift  deposits  bordering  modern  glaciers  re- 
semble the  heaps  of  debris  as  they  were  left  in  this  region.  But  the 
minor  inequalities  have  been'  reduced  in  the  process  of  soil  making,. 
or  by  the  work  of  rain  and  running  water.  The  larger  features  such  as 
the  hills  or  mounds  and  the  larger  depressions  remain. 

The  broad  open  valley  west  of  the  lake  ridge  is  not  the  result  of 
erosion  since  the  drift  was  deposited,  but  is'  a  great  depression  left  in 
the  surface  of  the  drift  when  the  ice  retreated.  All  of  the  ravines  and 
valleys  leading  directly  to  the  lake  have  been  developed  since  the  drift 
was  deposited  and  are  the  result  of  rain  water  running  off  over  the 
slope. 

Origin  of  a  Gully — When  the  ice  melted,  the  upland  extended  far- 
ther to  the  east  and  presumably  descended  gradually  to  the  level  of  the 
lake  (Plate  VIII,  Fig.  A.)  As  the  rain  fell  upon  this  new  land,  a  part 
of  the  water  sank  in,  a  part  was  evaporated,  some  collected  in  hollows 
or  undrained  depressions  on  the  surface  and  the  remainder  ran  off 
over  the  surface.  The  land,  it  is  fair  to  assume,  did  not  have  an  equal 
or  uniform  slope  to  the  lake  at  all  places,  nor  was  the  material  over  any 
considerable  area  perfectly  homogeneous.  The  surface  water  tended  to 
gather  in  the  depressions  of  the  surface,  however  slight  they  were. 
This  tendency  is  shown  on  almost  every  hillside  during  and  after  any 
considerable  shower.  The  water  concentrated  in  the  depressions  is  in 
excess  of  that  flowing  over  other  parts  of  the  surface  and  therefore 
flows  faster.  Flowing  faster,  it  erodes  the  surface  over  which  it  flows 
more  rapidly,  and  as  a  result  the  initial  depressions  are  deepened,  and 
washes  or  gullies  are  started.     (See  PI.  VIII,  Fig.  A,  and  PI.  XL) 

Should  the  run-off  not  find  irregularities  of  slope,  it  would,  at  the 
outset,  fail  of  concentration ;  but  should  it  find  the  material  more  easily 
eroded  along  certain  lines  than  along  others,  the  lines  of  easier  wear 
would  become  the  sites  of  greater  erosion.  This  would  lead  to  the  de- 
velopment of  gullies,  that  is  to  irregularities  of  slope.  Either  inequality 
of  slope  or  material  may  therefore  determine  the  location  of  a  gully, 
and  one  of  these  conditions  is  indispensable. 


*  In  the  preparation  of  this  portion  of  the  text  free  use  has  been  made  of  similar  matter  in 
Bull.  V,  Wisconsin  Geol.  and  Nat.  Hist.  Surv.,  by  Salisbury  and  Atwood. 


70  THE   EVANSTON-WAUKEGAN    REGJON.  Lbuli,.  7 

Once  started,  each  wash  or  gully  becomes  the  cause  of  its  own  growth, 
for  the  gully  developed  by  the  water  of  one  shower,  determines  greater 
concentration  of  water  during  the  next.  Greater  concentration  means 
faster  flow,  faster  liow  means  more  rapid  wear,  and  this  means  corres- 
ponding enlargement  of  tlie  depression  through  which  the  flow  takes 
place.  The  enlargement  effected  by  successive  showers  affects  a  gully 
in  all  dimensions.  The  water  coming  in  at  its  head  carries  the  head 
back  into  the  land  (head  erosion),  thus  lengthening  the  gully;  the 
water  coming  in  at  its  sides  wears  back  the  lateral  slopes,  thus  widening 
it;  and  the  water  flowing  along  its  bottom  deepens  it.  Thus  gullies 
grow  to  be  ravines  and  farther  enlargement  by  the  same  processes  con- 
verts ravines  into  valleys.  A  river  valley  therefore  is  often  but  a  gully 
grown  big. 

The  Course  of  a  Valley. — In  the  lengthening  of  a  gully  or  valley 
headward,  the  growth  will  be  in  the  direction  of  greatest  wear.  Thus, 
in  Plate  VIII,  Fig.  A,  if  the  water  coming  in  at  the  head  of  the  gully 
effects  most  wear  in  the  direction  A,  the  head  of  the  gully  will  advance 
in  that  direction;  if  there  be  most  wear  in  the  direction  B  or  C,  the 
head  will  advance  toward  one  of  these  points.  The  direction  of  greatest 
wear  will  be  determined  either  by  the  slope  of  the  surface,  or  by  the 
nature  of  the  surface  material.  The  slope  may  lead  to  the  concentra- 
tion of  the  entering  waters  along  one  line,  and  the  surface  material 
may  be  less  resistant  in  one  direction  than  in  another.  If  these  factors 
favor  the  same  direction  of  head-growth,  the  lengthening  will  be  more 
rapid  than  if  but  one  is  favorable.  If  there  be  more  rapid  growth 
along  two  lines,  as  B  and  C,  than  between  them,  two  gullies  may  de- 
velop. The  frequent  and  tortuous  windings  common  to  ravines  and 
valleys  are  therefore  to  be  explained  by  the  inequalities  of  slope  or 
material  which  affected  the  surface  while  the  valley  was  developing. 

Tributary  Valleys. — Following  out  this  simple  conception  of  valley 
growth,  we  have  to  inquire  how  a  valley  system  (a  main  valley  and 
its  tributaries)  is  developed.  The  conditions  which  determine  the  loca- 
tion and  development  of  gullies  on  a  new  land  surface,  determine  the 
location  and  development  of  tributary  gullies.  In  flowing  over  the  side 
slopes  of  a  gully  or  ravine,  the  water  finds  either  slope  or  surface 
material  failing  of  uniformity.  Both  conditions  lead  to  the  concen- 
tration of  the  water  along  certain  lines,  and  concentration  of  flow  on 
the  slope  of  an  erosion  depression,  be  it  valley  or  gully,  leads  to  the 
development  of  a  tributary  depression.  In  its  growth,  the  tributary 
repeats,  in  all  essential  respects,  the  history  of  its  main.  It  is  length- 
ened headward  by  water  coming  in  at  its  upper  end,  is  widened  by 
side  wash,  and  deepened  by  the  downward  cutting  of  the  water  which 
flows  along  its  axis.  The  factors  controlling  its  development  are  the 
same  as  those  which  controlled  the  valley  to  which  it  is  tributary. 

There  is  one  peculiarity  of  the  courses  of  tributaries  which  deserves 
mention.  Tributaries,  as  a  rule,  join  their  mains  with  an  acute  angle 
up-stream.  In  general,  new  land  surfaces,  such  as  are  now  under  con- 
sideration, slope  toward  the  sea  or  some  large  body  of  water.  If  a 
tributary  gully  were  to  start  back  from  its  main  at  right  angles,  more 


atwood.J  DEVELOPMENT   OF    RAVINES.  71 

water  would  come  in  on  the  side  away  from  the  shore,  on  account  of 
the  seaward,  or,  as  in  the  North  Shore  region,  the  lakeward  slope  of 
the  land.  This  would  be  true  of  the  head  of  the  gully  as  well  as  of 
other  portions,  and  the  effect  would  be  to  turn  the  head  more  and  more 
toward  parallelism  with  the  main  valley.  Local  irregularities  of  sur- 
face may,  and  frequently  do,  interfere  with  these  normal  relations,  so 
that  the  general  course  of  a  tributary  is  occasionally  at  right  angles  to 
its  main.  Still  more  rarely  does  the  general  course  of  a  tributary  make 
an  acute  angle  with  its  main  on  the  downstream  side.  Local  irregulari- 
ties of  surface  determine  the  windings  of  a  tributary,  so  that  their 
courses  for  longer  or  shorter  distances  may  be  in  violation  of  the 
general  rule.  This  case  is  well  illustrated  by  the  first  tributary,  from 
the  lake,  on  the  south  side  of  Pettibone  creek,  near  North  Chicago  ( Fig. 
48).  This  tributary  leads  toward  the  lake  joining  the  main  at  an 
acute  angle  down  stream.  The  encroachment  by  the  waves  has  carried 
away  the  head  of  the  gully  and  left  a  V-shaped  notch  in  the  cliff  from 
which  the  drainage  is  inland. 

On  the  whole,  the  valleys  of  a  system,  whose  history  has  not  been 
interrupted,  in  a  region  where  the  surface  material  is  not  notably 
heterogeneous,  follow  the  course  indicated  above.  This  more  general 
case  is  illustrated  by  nearly  every  drainage  system  along  the  shore 
from  Winnetka  to  the  Illinois-Wisconsin  line. 

How  a  Valley  Gets  a  Stream. — Valleys  may  become  somewhat  deep 
and  long  and  wide  without  possessing  permanent  streams,  though  from 
their  inception  they  have  temporary  streams,  the  water  for  which  is 
furnished  by  showers  or  melting  snows.  Yet  sooner  or  later,  valleys 
come  to  have  permanent  streams.  How  are  they  acquired?  Does  the 
valley  find  the  stream  or  does  the  stream  find  the  valley?  For  the 
answer  to  these  questions,  a  brief  digression  will  be  helpful. 

In  cultivated  regions,  wells  are  of  frequent  occurrence.  •  In  a  flat 
region  of  uniform  structure,  the  depth  at  which  well  water  may  be 
obtained  is  essentially  constant  at  all  points.     If  holes  (i  and  2,  Fig. 


5 ' A  £ 


Fig.  37.    Diagram  illustrating  the  relations  of  ground  water  in  streams. 

37)  be  excavated  below  this  level,  water  seeps  into  them,  and  in  a 
series  of  wells  the  water  stands  at  a  nearly  common  level.  This  means 
that  the  sub-structure  is  full  of  water  up  to  that  level.  These  relations 
are  illustrated  by  Fig.  37.  The  diagram  represents  a  vertical  section 
through  a  flat  region  from  the  surface  (s.  s.)  down  below  the  bottom 
of  wells.  The  water  stands  at  the  same  level  in  the  two  wells  and  the 
plane  through  them,  at  the  surface  of  the  water,  is  the  ground  water 
level.  If  in  such  a  surface  a  valley  were  to  be  cut  until  its  bottom  was 
below  the  ground  water  level,  the  water  would  seep  into  it,  as  it  does 
into  the  wells ;  and  if  the  amount  were  sufficient,  a  permanent  stream 
would  be  established.     This  is  illustrated  in  Fig.  37.     The  line  AA 


72  THE   EVANSTON-WAUKEG AN    REGION.  [bull.  7 

represents  the  ground  water  level,  and  the  level  at  which  the  water 
stands  in  the  wells,  under  ordinary  circumstances.  The  bottom  of  the 
valley  is  below  the  level  of  the  ground  water,  and  the  water  seeps  into 
is  from  either  side.  Its  tendency  is  to  fill  the  valley  to  the  level  AA. 
But  instead  of  accumulating  in  the  open  valley  as  it  does  in  the  en- 
closed wells,  it  flows  away,  and  the  ground  water  level  on  either  hand 
is  drawn  down. 

The  level  of  the  ground  water  fluctuates.  It  is  depressed  when  the  sea- 
son is  dry  (A'  A')  and  raised  when  precipitation  is  abundant  (A"  A"). 
When  it  is  raised,  the  water  in  the  wells  rises,  and  the  stream  in  the 
valley  is  swollen.  When  it  falls,  the  ground  water  surface  is  de- 
pressed, and  the  water  in  the  wells  becomes  lower.  If  the  water  surface 
sinks  below  the  bottom  of  the  wells,  the  wells  "go  dry;"  if  below  the 
bottom  of  the  valley,  the  valley  becomes,  for  the  time  being,  a  "dry 
run."  When  a  well  is  below  the  lowest  ground-water  level  its  supply 
of  water  never  fails,  and  when  the  valley  is  sufficiently  below  the  same 
level,  its  stream  does  not  cease  to  flow,  even  in  periods  of  drought. 
On  account  of  the  free  evaporation  in  the  open  valley,  the  valley  de- 
pression must  be  somewhat  below  the  level  necessary  for  a  well,  in 
order  that  the  flow  may  be  constant. 

It  will  be  seen  that  intermittent  streams,  that  is,  streams  which  flow 
in  wet  seasons  and  fail  in  dry,  are  intermediate  between  streams  which 
flow  after  showers  only,  and  those  which  flow  without  interruption. 
In  the  figure  the  stream  would  become  dry  if  the  ground  water  level 
sank  to  A'  A'. 

It  is  to  be  noted  that  a  permanent  stream  does  not  normally  precede 
its  valley,  but  that  the  valley,  developed  through  gully-hood  and 
ravine-hood  to  valley-hood  by  means  of  the  temporary  streams  sup- 
plied by  the  run-off  of  occasional  showers,  finds  a  stream,  just  as  dig- 
gers of  wells  find  water.  The  case  is  not  altered  if  the  stream  be  fed 
by  springs,  for  the  valley  finds  the  spring,  as  truly  as  the  well-digger 
finds  a  "vein"  of  water.  Most  of  the  North  Shore  gullies  have  but 
intermittent  streams.  A  few  are  deep  enough  or  have  found  a  suffi- 
cient number  of  springs  to  have  a  permanent  supply  of  water. 

Limits  of  a  Valley. — So  soon  as,  a  valley  acquires  a  permanent 
stream,  its  development  goes  on  without  the  interruption  to  which  it 
was  subject  while  the  stream  was  intermittent.  The  permanent  stream, 
like  the  temporary  one  which  preceded  it,  tends  to  deepen  and  widen 
its  valley,  and,  under  certain  conditions,  to  lengthen  it  as  well.  The 
means  by  which  these  enlargements  are  affected  are  the  same  as  be- 
fore. There  are  limits,  however,  in  length,  depth  and  width,  beyond 
which  a  vallev  may  not  go.  No  stream  can  cut  much  below  the  level 
of  the  water  into  which  it  flows,  and  it  can  cut  to  that  level  only  at 
its  outlet.  Up  stream  from  that  point  a  gentle  gradient  will  be  estab- 
lished over  which  the  water  will  flow  without  cutting.  In  this  condi- 
tion the  stream  is  at  grade.  Its  channel  has  reached  base  level;  that 
is,  the  level  to  which  the  stream  can  wear  its  bed.  This  grade  is, 
however,  not  necessarily  permanent,  for  what  was  base  level  for  a 
small  stream  in  an  early  stage  of  its  development  is  not  necessarily 
base  level  for  the  larger  stream  which  succeeds  it  at  a  later  time. 


atwood.]  DEVELOPMENT    OF    RAVINES.  73 


Fig.  38.  Diagram  showing  the  shifting  of  a  divide.  The  slopes  1A  and  IB  are  unequal.  The 
steeper  slope  is  worn  more  rapidly  and  the  divide  is  shifted  from  1  to  4,  where  the  two  slopes 
become  equal  and  the  migrating  of  the  divide  ceases. 

Weathering,  wash  and  lateral  corrasion  of  the  stream  coninue  to 
widen  the  valley  after  it  has  reached  base  level.  The  bluffs  of  valleys 
are  thus  forced  to  recede,  and  the  valley  is  widened  at  the  expense 
of  the  upland.  Two  valleys,  widening  on  opposite  sides  of  a  divide, 
narrow  the  divide  between  them  and  may  ultimately  wear  it  out. 
When  this  is  accomplished,  the  two  valleys  become  one.  The  limit 
to  which  a  valley  may  widen  on  either  side  is  therefore  its  neighbor- 
ing valley,  and  since,  after  two  valleys  have  become  one  by  the  elimin- 
ation of  the  ridge  between  them,  there  are  still  valleys  on  either  hand, 
the  final  result  of  the  widening  of  all  valleys  must  be  to  reduce  all 
the  area  which  they  drain  to  base  level.  As  this  process  goes  for- 
ward, the  upper  flat  into  which  the  valleys  were  cut  is  being  restricted 
in  area,  while  the  lower  flats  developed  by  the  streams  in  the  valley 
bottoms  are  being  enlarged.  Thus  the  lower  flats  grow  at  the  expense 
of  the  higher. 

There  are  also  limits  in  length  which  a  valley  may  not  exceed.  The 
head  of  any  valley  may  recede  until  some  other  valley  is  reached. 
The  recession  may  not  stop  even  there;  for  if,  on  opposite  sides  of  a 
divide,  erosion  is  unequal,  as  between  iA  and  iB,  Fig.  38,  the  divide 
will  be  moved  toward  the  side  of  less  rapid  erosion,  and  it  will  cease 
to  recede  only  when  erosion  on  the  two  sides  becomes  equal  (4A  and 
4B).  In  homogeneous  material  this  will  be  when  the  slopes  on  the 
two  sides  are  equal. 

It  should  be  noted  that  the  lengthening  of  a  valley  headward  is  not 
normally  the  work  of  the  permanent  stream,  for  the  permanent  stream 
begins  some  distance  below  the  head  of  the  valley.  At  the  head,  there- 
fore, erosion  goes  on  as  at  the  beginning,  even  after  a  permanent 
stream  is  acquired. 

Under  certain  circumstances,  the  valley  may  be  lengthened  at  its 
debouchure.  If  the  detritus  carried  by  it  is  deposited  at  its  mouth,  or 
if  the  sea  bottom  beyond  that  point  rise,  the  land  may  be  extended 
seaward,  and  over  this  extension  the  stream  will  find  its  way.  Thus  at 
their  lower,  as  well  as  at  their  upper  ends,  both  the  stream  and  its 
valley  may  be  lengthened. 

A  cycle  of  erosion. — If,  along  the  borders  of  a  new-born  land  area,  a 
series  of  valleys  were  developed,  essentialy  parallel  to  one  another, 
they  would  constitute  depressions  separated  by  elevations,  represent- 
ing the  original  surface  not  yet  notably  affected  by  erosion  (see  Plate 
VIII,  Fig.  B).  These  inter- valley  areas  might  at  first  be  wide  or 
narrow,  but  in  process  of  time  they  would  necessarily  become  narrow, 
for  once  a  valley  is  started,  all  the  water  which  enters  it  from  either 
side  helps  to  wear  back  its  slopes,  and  the  wearing  back  of  the  slopes 


74  THE    EVANSTON-WAUKEGAN    REGION.  [BULL.  7 

means  the  widening  of  the  valleys  on  the  one  hand  and  the  narrowing 
of  the  inter-valley  ridges  on  the  other.  Not  only  would  the  water 
running  over  the  slopes  of  a  valley  wear  back  its  walls,  but  many  other 
processes  conspire  to  the  same  end.  The  wetting  and  drying,  the  freez- 
ing and  the  thawing,  the  roots  of  plants  and  the  boring  of  animals,  all 
tend  to  loosen  the  material  on  the  slopes  or  walls  of  the  valleys,  and 
gravity  helps  the  loosened  material  to  descend.  Once  in  the  valley 
bottom,  the  running  water  is  likely  to  carry  it  off,  landing  it  finally  in 
the  sea.  Thus  the  growth  of  the  valley  is  not  the  result  of  running 
water  alone,  though  this  is  the  most  important  single  factor  in  the 
process. 

Even  if  valleys  developed  no  tributaries  they  would,  in  the  course 
of  time,  widen  to  such  an  extent  as  to  nearly  obliterate  the  intervening 
ridges.  The  surface,  however,  would  not  easily  be  reduced  to  perfect 
flatness.  For  a  long  time  at  least  there  would  remain  something  of 
slope  from  the  central  axis  of  the  former  inter-stream  ridge  toward 
the  streams  on  either  hand ;  but  if  the  process  of  erosion  went  on  for  a 
sufficiently  long  period  of  time,  the  inter-stream  ridge  would  be  brought 
very  low,  and  the  result  would  be  an  essentially  flat  surface  between 
the  streams,  much  below  the  level  of  the  old  one. 

The  first  valleys  which  started  on  the  land  surface  (see  Plate  VIII, 
Fig.  B)  would  be  almost  sure  to  develop  numerous  tributaries.  Into 
tributary  valleys  water  would  flow  from  their  sides  and  from  their 
heads,  and  as  a  result  they  would  widen  and  deepen  and  lengthen  just 
as  their  mains  had  done  before  them.  By  lengthening  headward  they 
would  work  back  from  their  mains  some  part,  or  even  all  the  way 
across  the  divides  separating  the  main  valleys.  By  this  process  the 
tributaries  cut  the  divides  between  the  main  streams  into  shorter  cross 
ridges.  With  the  development  of  tributary  valleys  there  would  be  many 
lines  of  drainage  instead  of  two,  working  at  the  area  between  two 
main  streams.  The  result  would  be  that  the  surface  would  be  brought 
low  much  more  rapidly,  for  it  is  clear  that  many  valleys  within  the 
area  between  the  main  streams,  widening  at  the  same  time,  would 
diminish  the  aggregate  area  of  the  upland  much  more  rapidly  than 
two  alone  could  do. 

The  same  thing  is  made  clear  in  another  way.  It  will  be  seen  (Plate 
IX,  Figs.  A  and  B)  that  the  tributaries  would  presently  dissect  an 
area  of  uniform  surface,  tending  to  cut  it  into  a  series  of  short  ridges 
or  hills.  In  this  way  the  amount  of  sloping  surface  is  greatly  in- 
creased, and  as  a  result  every  shower  would  have  much  more  effect 
in  washing  loose  materials  down  to  lower  levels,  whence  the  streams 
could  carry  them  to  the  sea. 

The  successive  stages  in  the  process  of  lowering  a  surface  are  sug- 
gested by  Fig.  39,  which  represents  a  series  of  cross  sections  of  a  land 
mass  in  process  of  degradation.  The  uppermost  section  represents  a 
level  surface  crossed  by  young  valleys.  The  next  lower  represents  the 
same  surface  at  a  later  stage,  when  the  valleys  have  grown  larger,, 
while  the  third  and  succeeding  sections  represent  still  later  stages  in  the 
process  of  degradation.  Plate  VIII,  Fig.  B,  and  Plate  IX,  Figs.  A 
and  B,  represent  in  another  way  the  successive  stages  of  stream  work 
in  the  general  process  of  degradation. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PL  9. 


Fig.  A.    The  same  valleys  as  shown  in  plate  8,  fig.  B,  in  a  later  stage  of  development. 
[Courtesy  of  Wisconsin  Geol.  Nat.  Hist.  Surv.] 


Fig.  B.    Same  valleys  as  shown  in  fig.  A  in  a  still  later  stage  of  development. 
[Courtesy  of  Wisconsin  Geol.  Nat.  Hist.  Surv.] 


atwood.]  DEVELOPMENT   OF    RAVINES.  75 

In  this  manner  a  series  of  rivers,  operating  for  a  sufficiently  long 
period  of  time,  might  reduce  even  a  high  land  mass  to  a  low  level, 
scarcely  above  the  sea.  The  new  level  would  be  developed  soonest 
near  the  sea,  and  the  areas  farthest  from  it  would  be  the  last — other 
things  being  equal — to  be  brought  low.  The  time  necessary 'for  the* 
development  of  such  a  surface  is  known  as  a  cycle  of  erosion  and  the, 
resulting  surface  is  a  base  level  plain;  that  is,  a  plain  as  near  sea  level 
as  river  erosion  can  bring  it.  At  a  stage  shortly  preceding  the  base 
level  sage  the  surface  would  be  a  peneplain.  A  peneplain,  therefore,  is 
a  surface  which  has  been  brought  toward,  but  not  to  base  level.  Land 
surfaces  are  often  spoken  of  as  young  or  old  in  their  erosion  history, 
according  to  the  stage  of  advancement  which  has  been  made  toward 
base  leveling.  Thus  the  Colorado  canyon,  deep  and  impressive  as  it 
is,  is,  in  terms  of  erosion,  a  young  valley,  for  the  river  has  done  but  a 
small  part  of  the  work  which  must  be  done  in  order  to  bring  its  basin 
to  base  level. 

Base  level  plains  and  peneplains. — It  is  important  to  notice  that  a 
plane  surface  (base  level)  developed  by  streams  could  only  be  devel- 
oped at  elevations  but  slightly  above  the  sea ;  that  is,  at  levels  at  which 
running  water  ceases  to  be  an  effective  agent  of  erosion;  for  so  long 
as  a  stream  is  actively  deepening  its  valley  its  tendency  is  to  roughen 
the  area  which  it  drains,  not  to  make  it  smooth.  The  Colorado  river, 
flowing  through  high  land,  makes  a  deep  gorge.  All  the  streams  "of  the 
western  plateaus  have  deep  valleys,  and  the  manifest  result  of  their 
action  is  to  roughen  the  surface.  The  ravines  of  the  North  Shore 
region  have  notably  roughened  the  topography  of  that  region.  Given 
time  enough,  and  the  streams  of  any  region  will  have  cut  their  beds 
to  low  gradients.  Then,  though  deepening  of  the  valleys  will  cease, 
widening  will  not;  and  inch  by  inch,  and  shower  by  shower,  the  ele- 
vated lands  between  the  valleys  will  be  reduced  in  area,  and  ultimately 
the  whole  will  be  brought  down  nearly  to  the  level  of  the  stream  beds. 
This  is  illustrated  by  Fig.  39. 

It  is  important  to  notice  further  that  if  the  original  surface  on 
which  erosion  began  is  level,  there  is  no  stage  intermediate  between 
the  beginning  and  the  end  of  an  erosion  cycle,  when  the  surface  is 
again  level,  or  nearly  so,  though  in  the  stage  of  a  cycle  next  preceding 
the  last — the  peneplain  stage  (fourth  profile,  Fig.  39) — the  surface- 
approaches  flatness.  It  is  also  important  to  notice  that  when  streams 
have  cut  a  land  surface  down  to  the  level  at  which  they  cease  to  erode 
that  surface  will  still  possess  some  slight  slope,  and  that  to  seaward. 
In  the  Evanston- Waukegan  region  the  streams  flowing  into  Lake  Mich- 
igan can  cut  no  lower  than  the  level  of  the  lake  and  the  base  level 
plain  to  which  they  are  tending  to  reduce  this  region  slopes  gently 
lakeward. 

No  definite  degree  of  slope  can  be  fixed  upon  as  marking  a  base 
level.  The  angle  of  slope  which  would  practically  stop  erosion  in  a 
region  of  slight  rainfall  would  be  great  enough  to  allow  of  erosion  if 
the  precipitation  were  greater.  All  that  can  be  said,  therefore,  is  that 
the  angle  of  slope  must  be  low.     The  Mississippi  has  a  fall  of  less 


76 


THE    EVANSTON-WAUKEGAN    REGION. 


Lbitll.  7 


Fig. 


Cross  sections  showing  various  stages  of  erosion  in  one  cycle. 


than  a  foot  per  mile  for  some  hundreds  of  miles  above  the  gulf.  A 
small  stream  in  a  similar  situation  would  have  ceased  to  lower  its  chan- 
nel before  so  low  a  gradient  was  reached. 

Characteristics  of  Valleys  at  Various  Stages  of  Development. — In  the 
early  stages  of  its  development  a  depression  made  by  erosion  has  steep 
lateral  slopes,  the  exact  character  of  which  is  determined  by  many  Con- 
siderations. Its  normal  cross  section  is  usually  described  as  V-shaped 
(Plate  XI  and  Fig.  40).  In  the  early  stages  of  its  development,  espe- 
cially if  in  unconsolidated  material,  the  slopes  are  normally  convex  in- 
ward. If  cut  in  solid  rock,  the  cross  section  may  be  the  same,  though 
many  variations  are  likely  to  appear,  due  especially  to  the  structure  of 
the  rock  and  to  inequalities  of  hardness.  If  a  stream  be  swift  enough 
to  carry  off  not  only  all  the  detritus  descending  from  its  slopes,  but 
to  abrade  its  bed  effectively  besides,  a  steep  sided  gorge  develops.  If 
it  becomes  deep,  it  is  a  canyon.  For  the  development  of  a  canyon,  the 
material  of  the  walls  must  be  such  as  is  capable  of  standing  at  a  high 
angle.  A  canyon  always  indicates  that  the  down  cutting  of  a  stream 
keeps  well  ahead  of  the  widening. 

The  profile  of  a  valley  at  the  stage  of  its  development  corresponding 
to  the  above  section  is  represented  diagrammatically  by  the  curve  A  B 
in  Fig.  41.  The  sketch  (PL  VIII,  Fig.  A)  represents  a  bird's  eye  view 
of  valleys  in  the  same  stage  of  development. 

At  a  stage  of  development  later  than  that  represented  by  the 
V-shaped  cross  section  the  corresponding  section  is  U-shaped,  as  shown 
in  Fig.  42.  The  same  form  is  shown  in  Plate  X,  Fig.  A.  This  repre- 
sents a  stage  of  development  where  detritus  descending  the  slopes  is 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.  10 


Fig.  A.    North  fork  of  Feltibone  creek,  North  Chicago. 


2s, 

Tr7"'/ 

■ 

^^^^J^- 

/  ■  _            -     jfc" 

InSS" 

rr 

^JL— -■ 

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% 

SS"**: 

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■ 

Fig.  B.    A  broad  open  valley  north  of  Kenosha,  Wis.    [Courtesy  of  C.  &  N.  W.  Ry.] 


ATWOOD.] 


DEVELOPMENT   OF    RAVINES. 


77 


not  all  carried  away  by  the  stream,  and  where  the  valley  is  being 
widened  faster  than  it  is  deepened.  Its  slopes  are  therefore  becoming 
gentler.  The  profile  of  the  valley  at  this  stage  would  be  much  the 
same  as  that  in  the  preceding,  except  that  the  gradient  in  the  lower  por- 
tion would  be  lower. 


Fig.  40.     Diagrammatic  oross  section  of  a  young  valley  corresponding  with  the  view 
•  shown  in  Plate  XI. 


Fig.  41.    Diagrammatic  profile  of  a  young  valley. 


Pig.  42. 


Diagrammatic  cross  section  of  a  valley  at  a  stage  corresponding  with  that 
shown  in  plate  X,  fig.  A. 


Fig.  43. 


Diagrammatic  cross  section  of  a  vailey  at  a  stage  Hater  than  that  shown  in  fig.  42, 
and  corresponding  with  the  view  shown  in  plate  X.  fig.  B. 


Still  later  the  valley  assumes  the  shape  shown  in  Plate  X,  Fig.  B,  and 
the  cross  section  shown  in  Fig.  43.  This  transformation  is  effected 
partly  by  erosion  and  partly  by  deposition  in  the  valley.  When  a 
stream  has  cut  its  valley  as  low  as  conditions  allow,  it  becomes  sluggish. 
A  sluggish  stream  is  easily  turned  from  side  to  side;  and  directed 
against  its  banks,  it  may  undercut  them,  causing  them  to  recede  at  th£ 
point  of  undercutting.  In  its  meanderings  it  undercuts  at  various  points 
at  various  times,  and  the  aggregate  result  is  the  widening  of  the  valley. 
By  this  process  alone  the  stream  would  develop  a  flat  at  grade.  At  the 
same  time  all  the  drainage  which  comes  in  at  the  sides  tends  to  carry 
the  walls  of  the  valley  farther  from  its  axis. 

A  sluggish  stream  is  also  generally  a  depositing  stream.  Its  deposits 
tend  to  aggrade  (build  up)  the  flat  which  its  meanderings  develop. 
When  a  valley  bottom  is  built  up  it  becomes  wider  at  the  same  time, 
for  the  valley  is,  as  a  rule,  wider  at  any  given  level  than  at  any  lower 


78 


THE   EVANSTON-WAUKEGAN    REGION. 


I  BULL.   7 


one.  Thus  the  U-shaped  valley  is  finally  converted  into  a  valley  with 
a  flat  bottom,  the  flat  being  due  in  large  part  to  erosion  and  in  smaller 
part  to  deposition.  Under  exceptional  circumstances  the  relative  im- 
portance of  these  two  factors  may  be  reversed. 


Contow     interval      10    feet 

Fig.  44.    Topographic  map  of  a  part  of  the  North  Shore  near  Ravinia,  showing  several 

young  vaileys. 


•  It  will  be  seen  that  the  cross  section  of  a  valley  affords  a  clue  to  its 
age.  A  valley  without  a  flat  is  young,  and  increasing  age  is  indicated 
by  increasing  width.  Valleys  illustrating  many  stages  of  development 
are  to  be  found  in  the  Evanston-Waukegan  region.  The  gullies  and 
ravines  represent  extreme  youth  (Fig.  44).  An  intermediate  stage 
of  development  is  shown  in  the  valley  of  Pettibone  creek  (Plate  X, 
Fig.  A),  North  Chicago,  and  in  the  valley  of  Dead  river  west  of 
Camp  Logan.  Old  age  is  not  illustrated  in  the  region,  for  there  has  not 
been  sufficient  time  since  the  ice  melted  for  valleys  to  have  reached 
that  stage  in  a  region  where  there  is  so  much  material  to  be  removed. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.  11. 


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atwood.]  DEVELOPMENT   OF    BA VINES.  79 

Transportation  and  Deposition. — Sediment  is  carried  by  streams  in 
two  ways:  (i)  By  being  rolled  along  the  bottom,  and  (2)  by  being 
held  in  suspension.  Dissolved  mineral  matter  (which  is  not  sediment) 
is  also  carried  in  the  water.  By  means  of  that  rolled  along  the  bottom 
and  carried  in  suspension,  especially  the  former,  the  stream,  as  already 
stated,  abrades  its  bed. 

The  transporting  power  of  a  stream  of  given  size  varies  with  its 
velocity.  Increase  in  the  declivity  or  the  volume  of  a  stream  increases 
its  velocity  and  therefore  its  transportive  power.  The  transportation 
effected  by  a  stream  is  influenced  (1)  by  its  transporting  power  and 
(2)  by  the  size  and  amount  of  material  available  for  carriage.  Fine 
material  is  carried  with  a  less  expenditure  of  energy  than  an  equal 
amount  of  coarse.  With  the  same  expenditure  of  energy,  therefore,  a 
stream  can  carry  a  greater  amount  of  the  former  than  of  the  latter. 

Since  the  transportation  effected  by  a  stream  is  dependent  on  its 
gradient,  its  size  and  the  size  and  amount  of  material  available,  it  fol- 
lows that  when  these  conditions  change  so  as  to  decrease  the  carrying 
power  of  the  river,  deposition  will  follow  if  the  stream  was  previously 
fully  loaded.  In  other  words,  a  stream  will  deposit  when  it  becomes 
overloaded. 

Overloading  may  come  about  in  the  following  ways:  (1)  By  de- 
crease in  gradient,  checking  velocity  and  therefore  carrying  power; 
(2)  by  decrease  in  amount  of  water,  which  may  result  from  evapora- 
tion, absorption,  etc. :  (3)  by  change  in  the  shape  of  the  channel,  so 
that  the  friction  of  flow  is  increased,  and  therefore  the  force  available 
for  transportation  lessened  ;  (4)  by  lateral  drainage  bringing  in  more 
sediment  than  the  main  stream  can  carry:  (5)  by  change  in  the  char- 
acter of  the  material  to  which  the  stream  has  access,  for  if  it  becomes 
finer,  the  coarse  material  previously  carried  will  be  dropped  and  the 
fine  taken ;  and  (6)  by  the  checking  of  velocity  when  a  stream  flows 
into  a  body  of  standing  water. 

Topographic  forms  resulting  from  stream  deposition. — The  topo- 
graphic forms  resulting  from  stream  deposition  are  various.  At  the 
bottoms  of  steep  slopes,  temporary  streams  build  alluvial  fans.  These 
are  commonly  developed  at  the  base  of  the  lake  cliff  (Plate  XI). 
Along  its  flood  plain  portion  a  stream  deposits  more  or  less  sediment 
on  its  flats.  The  part  played  by  deposition  in  building  a  river  flat  has 
already  been  alluded  to.  A  depositing  stream  often  wanders  about  in 
an  apparently  aimless  way  across  its  flood  plain.  At  the  bends  in  its 
course  cutting  is  often  taking  place  on  the  outside  of  a  curve  while 
deposition  i>  going  on  in  the  inside.  The  valleys  of  Pettibone  creek 
near  North  Chicago,  and  of  Dead  river  near  Camp  Logan,  illustrate 
this  process  of  cutting  and  building  in  the  flood  plain. 

Besides  depositing  on  its  flood  plain,  a  stream  often  deposits  in  its 
channel.  Any  obstruction  of  a  channel  which  checks  the  current  of  a 
loaded  stream  occasions  deposition.  In  this  way  "bars"  are  formed. 
Once  started  the  bar  increases  in  size,  for  it  becomes  an  obstacle  to 
flow,  and  so  the  cause  of  its  own  growth.  Tt  may  be  built  up  nearly 
to  the  surface  of  the  stream  and  in  low  water  it  may  become  an  island 
by  the  depression  of  the  surface  water. 


80  THE   EVANSTON-WAUKEGAN    REGION.  [bull.  7 

At  their  debouchures  streams  give  up  their  loads  of  sediment. 
Under  favorable  conditions  deltas  are  built.  The  material  carried  to 
the  lake  in  the  region  under  consideration  is  distributed  along  the 
shore  by  the  waves  and  currents  and  therefore  no  deltas  of  notable 
size  are  developed. 

Rejuvenation  of  Streams. — After  the  development  of  a  base  level 
plain  its  suriace  would  suffer  little  change  (except  that  effected  by 
underground  water)  so  long  as  it  maintained  its  position.  But  if,  after 
its  development,  a  base  level  plain  were  elevated  relative  to  sea  level, 
the, old  surface  in  a  new  position  would  be  subject  to  a  new  series  of 
changes  identical  in  kind  with  those  which  had  gone  before.  The  ele- 
vation would  give  the  established  streams  greater  fall  and  they  would 
re-assume  the  characteristics  of  youth.  The  greater  fall  would  acceler- 
ate their  velocities,  the  increased  velocities  would  entail  increased  ero- 
sion, increased  erosion  would  result  in  the  deepening  of  the  valleys,  and 
the  deepening  of  the  valleys  would  lead  to  the  roughening  of  the 
surface.  But  in  the  course  of  time  the  rejuvenated  streams  would  cut 
their  valleys  as  low  as  the  new  altitude  of  the  land  permitted ;  that  is, 
to  a  new  base  level.  The  process  of  deepening  would  then  stop  and  the 
limit  of  vertical  relief  which  the  streams  were  capable  of  developing 
would  be  attained.  But  the  valleys  would  not  stop  widening  when  they 
stopped  deepening,  and  as  they  widened  the  intervening  divides  would 
become  narrower  and  ultimately  lower.  In  the  course  of  time  they 
would  be  destroyed,  giving  rise  to  a  new  level  surface  much  below  the 
old  one,  but  developed  in  the  same  position  which  the  old  one  occupied 
when  it  originated;  that  is,  a  position  but  little  above  sea  level. 


Fig.  45.     Diagrammatic  cross-section  illustrating  the  topographic  effect  of  rejuvenation 
by  uplift.    Compare  with  Fig.  A,  Plate  XIII. 

If  at  some  intermediate  stage  in  the  development  of  a  second  base- 
level  plain,  say  at  a  time  when  the  streams  had  half  completed  their 
work,  rejuvenation  by  uplift  were  to  occur,  the  half  completed  cycle 
would  be  brought  to  an  end  and  a  new  one  begun.  The  streams  would 
again  be  quickened,  and  as  a  result  they  would  promptly  cut  new  and 
deeper  channels  in  the  bottoms  of  the  great  valleys  which  had  already 
been  developed.  The  topography  which  would  result  is  suggested  by 
the  above  diagram  (Fig.  45),  which  illustrates  the  cross  section  which 
would  be  found  after  the  following  sequence  of  events :  ( I )  The  de- 
velopment of  a  base  level,  A  A;  (2)  uplift,  rejuvenation  of  the  streams 
and  a  new  cycle  of  erosion  half  completed,  the  new  base  level  being  at 
B  B;  (3)  a  second  uplift,  bringing  the  second  (incomplete)  cycle  of 
erosion  to  a  close,  and  by  rejuvenating  the  streams  inaugurating  the 
third  cycle.  As  represented  in  the  diagram,  the  third  cycle  has  not 
progressed  far,  being  represented  only  by  the  narrow  valley,  C.  The 
base  level  is  now  2-2,  and  the  valley  represented  in  the  diagram  has 
not  yet  reached  it.     (Compare  with  Fig.  A,  Plate  XIII.) 


atwood.J  DEVELOPMENT   OF    RAVINES.  81 

The  rejuvenation  of  a  stream  shows  itself  in  another  way.  The  nor- 
mal profile  of  a  valley  bottom  in  a  non-mountainous  region  is  a  gentle 
curve,  concave  upward  with  gradient  increasing  from  debouchure  to 
source.  Such  a  profile  is  shown  in  Fig.  46.  Fig.  47,  on  the  other  hand, 
is  the  profile  of  a  rejuvenated  stream.    The  valley  once  had  a  profile 


5£A      LEVEL 


Fig.  46.    Normal  profile  of  a  valley  bottom  in  a  non-mountainous  region. 


Fig.  47.    Profile  of  a  stream  rejuvenated  by  uplift. 

similar  to  that  shown  in  Fig.  46.  Below  B  its  former  continuation  is 
marked  by  the  dotted  lines,  B  C.  Since  rejuvenation  the  stream  has 
deepened  the  lower  part  of  its  valley  and  established  there  a  profile  in 
harmony  with  the  new  conditions.  The  upper  end  of  the  new  curve 
has  not  yet  reached  beyond  B. 

The  Influence  of  the  Changes  in  the  Level  of  Lake  Michigan  in  Val- 
ley Development. — In  this  region  certain  of  the  older  streams  have 
been  rejuvenated,  not  by  an  uplift  of  the  land,  but  by  the  lowering  of 
Lake  Michigan.  The  lowering  of  the  lake  level  depressed  the  base  to 
which  the  streams  could  work,  and  therefore  quickened  the  downward 
cutting  in  the  valleys.  All  valleys  that  were  developed  before  the 
subsidence  of  the  lake  waters  must  have  been  affected  by  this  change. 
The  narrow,  V-shaped  gullies  continued  to  grow  deeper,  but  did  not 
essentially  change  in  form.  In  valleys  which  had  broad,  flat  bottoms 
at  the  time  of  the  lowering  of  the  lake,  the  deepening  of  the  channel 
left  the  former  bottom  lands  as  terraces.  These  terraces  grew  smaller 
as  the  rejuvenated  streams  developed  their  new  or  inner  valleys,  and 
unless  broad  to  begin  with  could  not  be  expected  to  remain  until  today. 
In  a  few  of  the  larger  valleys  such  terraces  have  been  identified.  In 
Pettibone  creek  terrace  remnants  occur  at  several  places  in  the  valley 
(Fig.  48).  The  best  preserved  remnant  is  in  the  lower  portion  of  the 
valley  on  the  north  side  of  the  stream.  This  terrace  is  forty  feet  above 
the  present  lake  level  (C-T,  Fig.  48).  Following  up  stream,  several 
remnants  of  the  forty-foot  terrace  occur.  They  vary  in  width  up  to 
300  feet  and  their  surfaces  retain  the  characteristic  abandoned  chan- 
nels of  old  flood  plains.  This  terrace  corresponds  in  elevation  to  the 
Calumet  stage  of  Lake  Chicago. 

Twenty  feet  above  the  stream,  and  about  twenty-five  feet  above  the 
present  lake  level,  there  are  several  distinct  terrace  remnants.  These 
correspond  with  the  Upper  Toleston  stage.  In  the  area  shown  on  Fig. 
48  one  such  remnant  (T-T)  is  brought  out  by  the  ten-foot  contour 
map.     Several  other  small  remnants  at  the  Upper  Toleston  level  may 

—6  G 


82 


THE   EVANSTON-WAUKEGAN    REGION. 


[bull.  7 


be  recognized  in  the  valley.  At  about  eight  feet  above  the  stream  and 
thirteen  feet  above  the  lake  there  are  several  benches  or  terrace-like 
remnants  (L-T)  that  correspond  to  the  Lower  Toleston,  or  Nipissing 
stage. 


Fig.  48.  Topographic  map  of  the  lower  portion  of  Pettibone  Creek  valley  near  North 
Chicago,  by  Fred  Kay  and  F.  D.  Mabrey.  A  broad  terrace  (C-T)  corresponding  to  the  Calumet 
stage  of  Lake  Chicago  is  shown  on  the  North  side  of  the  valley.  In  the  bottom  of  the  valley 
small  remnants  (T-T)  correspond  to  the  upper  Toleston,  and  (L-T)  to  the  lower  Toleston 
stages  of  Lake  Chicago. 


The  mouth  of  Pettibone  creek  is  one  of  the  most  interesting  physio- 
graphic laboratories  of  the  North  Shore  region.  The  view  shown  in 
Plate  XII  reproduces  the  conditions  as  they  existed  at  one  time,  and 
may  be  taken  as  an  illustration  of  the  educational  value  of  a  visit  to 
such  a  place.  In  the  foreground  there  is  a  sand  and  gravel  pit,  which  is 
being  developed  by  a  shore  current  set  up  by  a  southeasterly  wind. 
The  growth  of  the  spit  is  diverting  the  stream  northward.  The  stream 
channel  across  the  beach  indicates  by  its  structure  that  the  beach  mate- 
rial formerly  (probably  but  a  few  days  preceding  the  date  of  the 
photograph)  blocked  the  outlet.  Strong  east  or  northeast  winds  may 
account  for  such  an  accumulation.   The  sands  and  gravels  blocked  the 


- 


DEVELOPMENT   OF    RAVINES. 


83 


outlet  of  the  stream.     The  ponded  waters  rose,  formed  a  considerable 
lake  and  overflowed.     When  the  outlet  of  the  valley  lake  was  estab- 
lished, the  waters  of  Lake  Michigan  were  two  to  three  feet  higher  on 
this  side  of  the  lake  than  when  the  picture  was  taken,  for  the  outlet 
stream  failed  at  that  time  to  cut  as  low  as  at  present.     This  is  shown 
in  the  small  terrace   in  the  channel   across   the   beach.     The  terrace 
corresponds  to  and  is  continuous  with  the  miniature  wave-cut  terrace 
at  the  base  of  the  small  cliff  in  the  sand  and  gravel  on  the  beach.   When 
the  lake  subsided  from  the  sand  and  gravel  cliff  the  stream  was  able 
to  cut  lower  and  entrenched  its  course  to  the  depth  shown  in  the  view. 
Each  time  that  the  level  of  Lake  Michigan  changed*  the  streams  in 
the  bordering  lands  were  affected.    When  the  lake  level  fell  the  streams 
were  quickened  and  valley  deepening  was  augmented   (Fig.  A,  Plate 
XIII).     When  the  lake  level   rose  the  lower  portions  of  the  valleys 
must  have  been  drowned  by  the  advancing  lake  waters.     The  streams 
lost  velocity  and  began  to  fill  or  silt  up  their  valleys.    Examples  of  such 
filling  are  known  in  the  larger  valleys  leading  to  Lake  Michigan  in 
Wisconsin.     No  good  case  is  known  in  the  Evanston-Waukegan  area, 
but  the  valley  of  Dead  river  west  of  Camp  Logan  may  have  had  such  a 
history.     There  are  at  least  eight  feet  of  alluvium  in  the  lower  portion 
of  the  valley,  just  west  of  the  station.    Furthermore,  the  broad  flat-bot- 
tomed form  of  the  valley  suggests  that  it  has  been  partially  filled  with 
silts.     The  valley  is  larger  than  those  developed  by  similar  streams 
since  the  re-advance  of  the  lake  waters  in  Calumet  times,  and  there- 
fore would  seem  to  have  had  a  longer  history.     When  the  excavations 
are  made  at  the  mouth  of  Pettibone  creek,  in  constructing  a  harbor  for 
the  United   States  naval  training  station,  some  interesting  exposures 
are  likelv  to  be  made. 


Fig.  49.  Topographic  sketch  map  of  one  of  the  head  waters  of  Dead  River  between 
Waukegan  and  Beach.  A,  the  present  outlet;  B,  a  possible  former  outlet;  near  C  the  original 
outlet. 


One  of  the  tributaries  of  Dead  river  between  Waukegan  and  Beach 
has  had  a  curious  and  interesting  history.  This  valley  trends  south- 
ward on  the  west  side  of  the  Glenwood  beach  for  some  distance,  and 
then  turns  sharply  to  the '  east,  crossing  the  ancient  shore  lines  and 
opening  into  the  lake  flat.  The  topographic  sketch  map  (Fig.  49) 
—  $ 

*  The  changes  of  lake-level  are  given  in  pp.  54-68. 


84  THE   EVANSTON-WAUKEGAN   REGION.  Lbull.  7 

shows  the  general  form  of  the  valley,  the  present  outlet  of  the  stream 
A,  the  ancient  outlet  near  C\  and  a  possible  former  outlet  at  B.  The 
location  of  the  Glenwood  and  lower  Toleston  shore  lines  are  also  shown 
in  the  figure.  Up  stream  from  A  the  valley  has  a  sharp  inner  gorge  or 
trench  cut  below  well  marked  Calumet  and  Toleston  terraces.  It  is 
evident,  therefore,  that  this  portion  of  the  valley  was  well  developed 
during  the  Calumet  stage  of  Lake  Chicago ;  that  when  the  lake  waters 
fell  to  the  Toleston  level  the  valley  bottom  was  appropriately  lowered, 
and  when  the  outlet  at  A  was  established  the  stream  began  cutting  the 
inner  trench. 

Down  the  main  valley  from  outlet  A  the  higher  Toleston  level,  about 
twenty-five  feet  above  Lake  Michigan,  is  well  developed.  It  is  evident 
that  this  valley  bottom  was  reduced  about  as  far  as  was  possible  during 
that  time,  and  that  a  considerable  flood  plain  was  developed.  In  this 
portion  of  the  valley  there  are  also  remnants  of  the  lower  Toleston  flood 
plain.  This  means  that  the  stream  occupied  this  portion  during  a 
part  at  least  of  the  lower  Toleston  time.  Therefore,  the  diversion  of  the 
head  waters  through  outlet  A  did  not  occur  until  late  in  Toleston  time. 

Between  C  and  C  there  are  terrace  remnants  that  appear  to  be  por- 
tions of  old  flood  plains.  This  indicates  that  the  valley  extended  south- 
ward from  outlet  C  and  that  the  east  side  of  the  valley  has  since  been 
removed  by  wave  cutting. 

The  sharp  cliff  shown  in  Fig.  49,  west  of  the  railroad,  was  developed 
by  the  waters  of  Lake  Nipissing  rising  to  the  lower  Toleston  level. 
These  waters  cut  away  the  east  side  of  the  valley  between  C  and  C 
and  norrowed  the  morainic  belt  north  of  C  and  east  of  the  valley.  At 
A  and  B  the  valley  swung  to  the  east,  and  at  these  places  the  east 
wall  became,  very  narrow.  Possibly  the  waves  succeeded  in  cutting 
through  to  the  valley  at  A  and  B  somewhat  as  they  are  now  doing  at 
a  point  north  of  Kenosha,  Wis.*  There  the  flood  plain  is  essentially  at 
the  level  of  the  lake,  but  in  the  case  shown  in  Fig.  49  the  flood  plain 
where  the  capture  took  place  was  about  fifteen  feet  above  the  lake 
waters  at  that  time.  Possibly  the  actual  capture  of  the  stream  was 
accomplished  by  a  small  stream  working  headward  from  the  Nipissing 
cliff.  When,  by  one  or  the  other  of  these  ways,  the  outlet  A  was 
established,  the  stream  began  entrenching  its  course  above  that  point. 
If  outlet  B  was  ever  occupied  by  much  of  a  stream,  it  was  not  occupied 
by  such  a  Stream  very  long.  The  amount  of  cutting  at  that  point  is 
very  slight  Since  most  of  the  waters  are  diverted  at  A,  there  is  little 
outflow  now  at  C. 

*  Described  in  '  'Intercision,  a  peculiar  kind  of  modification  of  drainage.  "  by  J.  W.  Goldth- 
wait.     School  Sci.  and  Math.,  Vol.  VIII,  pp.  129-139.  February.  1908. 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PI.   \'.l. 


Fig.  A.      Little  Fort  creek  in  the  western  portion  of  Waukegan.      These  terraces  probably 
espond  to  the  Calumet  stage  of  Lake  Chicago  as  shown  in  the  valley  development. 


Sfcf*^2'"* 

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Fig.  U.    Glacial  bowlders  used  in  a  building. 


atwood.]  UNDERGROUND    WATER.  85 


UNDERGROUND  WATER. 
(by  w.  w.  atwood.) 

Shallow  Ground  Waters. — In  what  has  preceded,  reference  has  been 
made  only  to  the  results  accomplished  by  the  water  which  runs  off 
over  the  surface.  The  water  which  sinks  beneath  it  is,  however,  of  no 
small  importance  in  reducing  a  land  surface.  The  enormous  amount 
of  mineral  matter  in  solution  in  spring  water  bears  witness  to  the  effi- 
ciency of  the  ground  water  in  dissolving  rock,  for  since  the  water  did 
not  contain  the  mineral  matter  when  it  entered  the  soil,  it  must  have 
acquired  it  below  the  surface.  By  this  means  alone,  areas  of  more 
soluble  rock  are  lowered  below  those  of  less  solubility.  Furthermore., 
the  water  is  still  active  as  a  solvent  agent  after  a  surface  has  been 
reduced  to  so  low  a  gradient  that  the  run-off  ceases  to  erode  mechani- 
cally. 

The  seepage  of  ground  water  on  steep  valley  slopes  and  on  the  lake 
cliff  sometimes  saturates  the  glacial  clays  and  causes  them  to  flow. 
These  mud  streams  may  often  be  seen  near  Fort  Sheridan,  Highwood 
and  at  other  places  where  the  cliff  is  not  clothed  with  vegetation.  At 
places  the  addition  of  ground  water  to  the  clay  in  a  steep  bank  or  bluff 
so  increases  the  weight  of  the  mass  as  to  cause  landslides.  Such  land- 
slides are  well  known  in  the  southeast  portion  of  the  Fort  Sheridan 
grounds  on  the  modern  lake  bluff.  Sometimes  the  saturation  of  the 
clay  in  the  lake  and  valley  bluffs  causes  the  clay  to  become  so  slippery 
that  the  overlying  mass,  which  may  be  relatively  dry,  slides  off  and 
moves  for  some  distance  down  the  slope. 

In  the  farming  districts,  within  the  Evanston-Waukegan  area,  ground 
water  is  reached  in  the  common  wells  at  depths  varying  from  five  to 
ioo  feet.  At  some  places  the  glacial  drift  contains  very  little  water 
and  the  farmers  have  found  it  necessary  to  drill  into  the  bed-rock  for- 
mation to  secure  a  good  water  supply. 

Artesian  Wells. — The  village  of  Highland  Park,  the  city  of  Wauke- 
gan,  the  Northwestern  Railway  and  the  Corn  Products  Refining  Com- 
pany at  Waukegan,  and  numerous  private  citizens  in  the  North  Shore 
region,  have  artesian  wells. 

At  Highland  Park  the  public  well  is  1,590  feet  deep.  At  L.  E. 
Swift's,  Lake  Forest,  the  artesian  well  is  989  feet  deep.  At  Mr.  Booth's, 
Lake  Forest,  the  artesian  well  is  about  800  feet  deep.  At  Miss  Cul- 
ver's, Lake  Forest,  there  is  an  artesian  well  2,062  feet  deep.  In  South 
Evanston  there  is  an  artesian  well  1,748  feet  deep.     (Fig.  50.) 


86 


THE   EVANSTON-WAUKEGAN    REGION. 


[bull.  7 


There  are  two  horizons  from  which  the  artesian  water  supply  is 
obtained.  One  is  reached  at  about  800  feet  and  continues  downward 
for  about  400.  The  iower  horizon  is  reached  between  1,300  and  1,500 
feet  and  continues  several  hundred  feet.  The  lower  limit  of  this  horizon 
has  not  been  reached  in  the  region. 


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Pig.  50.    Artesian  well  section  in  South  Evanston  showing  the  formations  that  underlie 
the  entire  Evanston-Waukegan  region. 


The  waters  in  the  artesian  wells  are  supplied  by  the  rainfall  of  cen- 
tral Wisconsin.  The  formations  shown  in  Fig.  50  reach  the  surface 
in  that  region  and  descend  gradually  southward  and  southeastward 
under  the  Evanston-Waukegan  area  and  much  farther.  The  limestones 
overlying  the  St.  Peters  and  Potsdam  sandstones  are  relatively  imper- 
vious, and  the  waters  are  retained  in  the  porous  sandstone  layers  until 
the  overlying  beds  are  punctured.  The  outcropping  area  of  the  St. 
Peters  sandstone  in  Wisconsin  is  much  less  than  that  of  the  Potsdam 
(Fig.  51)  and  the  thickness  of  the  formation  is  also  less.  The  lower 
water  bearing  horizon  therefore  contains  a  much  larger,  supply  than 
the  upper. 

"Mr.  Leverett  has  made  the  following  report  on  wells  within  this 
region :  "At  Waukegan  the  public  water  supply  was  formerly  obtained 
from  artesian  wells,  but  since  1895  it  has  been  obtained  by  pumping 
from  Lake  Michigan.  Three  wells  were  sunk  to  depths  of  1,135,  1,600 
and  2,005,  respectively.  The  first  well  is  reported  by  Major  DeWolf 
to  have  obtained  water  of  fair  quality,  though  rather  heavily  charged 
with  iron.  The  second  well  obtained  an  unpleasant  water  with  bad 
odor,  thought  to  be  sulphurous.     The  wells  were  discontinued  because 


ATWOOD.] 


UNDERGROUND    WATER. 


87 


SCALE 


MILLS 


Fig.  51.    Main  absorbing  areas  for  the  Potsdam  and  St.  Peters  formations.    From  the 
17th  Ann.  Rep.  U.  S.  Geol.  Surv.,  Part  II.  pi.  CXI.  by  Frank  Leverett. 


of  the  hardness  of  the  water,  it  being  unfit  for  boiler  use.  The  water 
also  was  found  unsuitable  for  sprinkling  lawns,  it  being  destructive 
to  grass.  The  Lake  Michigan  water  is  not  too  hard  for  boiler  use  and 
in  other  ways  is  more  satisfactory  than  the  artesian  water.  The  present 
intake  is  at  a  distance  of  1,700  feet  from  the  shore,  but  it  is  proposed 
to  extend  the  tunnel  to  a  distance  of  about  a  mile. 

"At  Lake  Forest,  wells  which  yield  thirty  barrels  per  day  are 
usually  obtained  at  a  depth  of  forty  feet  or  less.  An  artesian  well  at 
the  residence  of  Hon.  C.  P.  Farwell  reached  a  depth  of  960  feet  and 
obtained  a  flow  of  water  whose  head  was  originally  fifty  feet  above 
the  surface,  or  about  125  feet  above  Lake  Michigan.  The  drift  at  this 
well  has  a  thickness  of  160  feet. 


88 


THE   EVANSTON^WAUKEGAN   REGION. 


[bull.  7 


"At  Highland  Park  there  are  four  artesian  wells  with  depths  of 
i, 800  to  2,200  feet.  Mr.  P.  T.  Dooley,  a  well  driller,  residing  at  this 
village,  reports  that  wells  five  inches  in  diameter  yield  about  150  gal- 
lons per  minute.  A  strong  flow  of  water  is  obtained  at  about  900  feet 
and  also  at  about  1,300  feet,  as  well  as  at  lower  horizons.  The  wells 
all  flowed  when  first  made,  but  at  present  scarcely  reach  the  surface. 
The  elevation  of  the  well  mouths  is  no  to  115  feet  above  Lake  Michi- 
gan, or  690  to  695  feet  above  the  sea.  The  thickness  of  drift  is  about 
175  feet." 

Tabulated  Artesian    Well  Data. 
(Compiled  from  Leverett's  Report.*) 


■ 

Locality  and  Owner.  , 

Altitude. 

Depth. 

Capacity 

per 
minute. 

Water  bed  and  veins. 

Evanston — city  well 

Feet.  , 
612 
685 

650+ 

600 
658 

Feet. 
1.602 
2,200 

960 

I       1.135     | 

{       1. 600     \ 

\       2,005     \ 

1.570 

Gallons. 

Limestone,  5C2-832  ft. 

Highland  Park— city  well 

Lake  Forest— C.  C.  Farwell 

Waukegan — old  waterworks . 

150 

60 

Galena,  900  ft. ;  Lower 
Magnesian  1,300  ft.; 
Potsdam  1700-2200  ft. 

Probably  St.  Peters 
sandstone 

Winnetka — Lloyd's  well 

150 

and  probably  Potsd. 

*  Loc.  cit.,  pp,  813-818. 

Altitude  of  Top  of  St.  Peters  Sandstone  in  Chicago  and  Evanston- 
Waukegan  Region. 

( Compiled  from  Leverett's  Report.*) 


Location. 

Altitude 
below  tide. 

Thickness 

Chicago 

Feet.    - 
225+ 
222 
320 
258 
281 

J 
200+ 

Evanston    

420  ? 

Highland  Park 

200 

Lake  Bluff 

167 

Winnetka. ...        

212 

The  surface  of  Lake  Michigan  is  581  feet  above  mean  sea  level. 
*  Loc.  cit.,  p.  795. 


atwood.]  GEOGRAPHIC   CONDITIONS    AND    SETTLEMENT.  89 


GEOGRAPHIC  CONDITIONS  AND  SETTLEMENT. 
(by  w.  w.  atwood.) 

History. — When  settlers  came  to  northeastern  Illinois  in  the  early 
part  of  the  last  century,  many  of  them  selected  the  North  Shore  region 
in  preference  to  the  Chicago  district.  The  old  settlers  who  live  in  the 
district  recall  the  days  when  Chicago  was  spoken  of  as  a  "mud  hole." 
The  site  of  Waukegan  was  selected  for  a  city  before  that  of  Chicago, 
and  a  small  village  and  fort  were  established  east  of  Highwood  near 
the  shore,  when  Chicago  was  little  more  than  a  trading  post.  The 
region  continues  to  be  very  attractive  for  suburban  homes,  and  large 
industrial  interests  have  been  established  at  Waukegan. 

Location  of  Roads. — Before  the  railroad  was  built  north  of  Chicago 
there  was  a  government  highway  from  Fort  Dearborn  to  Green  Bay 
known  as  the  Green  Bay  road.  The  location  of  this  road  was  con- 
trolled by  physiographic  conditions.  In  the  southern  portion  of  the 
district,  just  north  of  Chicago,  it  was  located  on  a  beach  ridge.  This 
old  shore  line  offered  an  even  grade  where  the  land  was  drier  than  on 
either  side,  and  where  the  road  material  was  sand  and  gravel.  The 
road  followed  the  ancient  shore  line  through  the  present  site  of  Evans- 
ton  to  the  southern  margin  of  Wilmette,  where  the  beach  ridge  comes 
to  the  modern  lake  cliff.  Ridge  road,  in  Evanston,  is  a  portion  of  the 
old  Green  Bay  road.  It  is  conspicuously  above  the  general  level  of  the 
lake  plain  and  the  homes  now  located  there  are  favored  by  a  good 
outlook  and  by  good  drainage  through  the  beach  material  away  from 
the  basements  and  cellars. 

Through  Wilmette  the  government  road  was  unfortunately  near  the 
lake  cliff  and  was  frequently  washed  away  by  the  waves.  At  the  foot 
of  Lake  avenue,  Wilmette,  as  reported  by  C.  P.  Westerfleld,  a  surveyor, 
at  Waukegan,  111.,  the  present  shore  line  is  nearly  300  feet  west  of 
where  it  was  in  1857.  The  original  location  of  the  old  government 
road  at  this  place  is  more  than  200  feet  east  of  the  present  shore  line. 

A  short  distance  north  of  Winnetka  the  Green  Bay  road  turned 
westward  to  avoid  crossing  the  numerous  ravines,  and  thence  northward 
near  the  present  line  of  the  Chicago  &  Northwestern  Railway.  The  old 
road  turned  westward  just  far  enough  to  reach  the  uneroded  rolling 
upland,  and  the  modern  steam  and  electric  roads  have  taken  advantage 
of  the  same  route  just  west  of  most  of  the  ravines.  The  railroads  have 
built  culverts  where  they  cross  the  heads  of  some  of  the  longer  ravines. 

The  Grosse  Point  road,  west  of  Evanston  and  Wilmette,  is  also  an 
old  highway,  and  was  located  on  a  beach  ridge  because  of  the  peculiar 


90 


THE   EVANSTON-WAUKEGAN    REGION. 


[bull.  7 


advantages  offered  by  the  sand  and  gravel.  In  the  Chicago  region 
there  are  several  other  illustrations  of  this  same  physiographic  control 
of  the  early  highways. 

The  roads  or  streets  in  the  most  recently  surveyed  village  in  the 
North  Shore  region  show  an  interesting  relationship  to  the  topography 
of  the  village  site.  In  the  southern  portion  of  Zion  City  there  are 
several  head-water  ravines  of  one  of  the  tributaries  of  Dead  river, 
and  the  influence  of  these  ravines  on  the  location  of  the  streets  is 
clearly  shown  in  Fig.  52.  A  similar  topographic  control  of  roads  is 
illustrated  in  Lake  Forest  and  to  some  extent  in  Highland  Park. 


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Fig.  52.    Road  map  of  the  southern  portion  of  Zion  City. 

Towns  and  Villages. — The  margin  of  the  lake  flat  where  the  rolling 
upland  begins  is  a  favorite  site  for  villages.  In  the  Chicago  region 
beginning  at  the  south,  Dyer,  Ind.,  Flossmoor,  Chicago  Heights, 
Homewood,  Palos  Springs,  Palos  Park,  LaGrange,  Galewood  and  Nor- 
wood Park  are  at  this  margin.  In  the  Evanston-Waukegan  region 
there  are  not  many  such  sites,  but  Winnetka  has  such  a  location  at 
the  south,  and  Waukegan  at  the  north.  The  opportunity  for  a  harbor, 
the  lake  flat  for  wharfs  and  industrial  plants,  and  the  upland  for  the 
home  district,  were  important  factors  that  influenced  the  selection  of 
the  Waukegan  site. 

Soils  and  Sub-soils. — When  the  great  ice  sheet  retreated  the  moraine 
deposits  were  exposed  to  the  processes  of  weathering  and  erosion. 
The  waters  that  went  below  the  surface  dissolved  some  of  the  mineral 
matter  in  the  drift.  Most  of  the  calcareous  material  in  the  upper  three 
to  five  feet  of  the  drift  has  now  been  leached  out.  The  clay  in  this 
upper  zone  usually  fails  to  respond  to  acid  as  Jess  exposed  clay  in  the 
region  will.  Expansion  and  contraction  due  to  changes  in  temperature 
loosened  the  material  and  made  it  more  porous.     The  freezing  and 


ILLINOIS  GEOLOGICAL  SURVEY. 


Bull.  No.  7,  PL  14. 


Fig.  A.    Truck  farm  near  Rogers  Park. 


Fig.  B. 


Site  of  the  town  of  St.  John,  showing  two  orchard  trees  that  were  in  the 
western  portion  of  the  town.     [Courtesy  of  C.  &  N.  W.  Ry.] 


atwood.J  GEOGRAPHIC   CONDITIONS    AND    SETTLEMENT.  91 

thawing  of  the  ground  water  also  left  the  land  less  compact.  For  two 
or  three  decades  after  the  retreat  of  the  ice,  judging  from  the  present 
condition  of  the  drift  heaps  along  the  Chicago  Drainage  Canal,  this 
region  was  essentially  barren.  As  plant  life  began  to  appear,  the 
growth  of  roots  assisted  in  loosening  the  ground,  and  the  decay  of 
vegetable  matter  contributed  to  the  surface  loam  or  sou.  The  decayed 
vegetable  matter  is  dark  brown  or  black,  and  today  affects  the  color 
of  the  uppermost  one  or  two  feet  in  every  exposure  in  the  drift  of  this 
region.  The  oxidation  of  the  iron-bearing  elements  in  the  drift  has 
given  to  the  five  to  ten  feet  underlying  the  soil  a  light  yellow  or  buff 
color. 

These  various  soil  making  processes  are  operative  on  the  lake  plain 
and  on  the  upland,  but  they  have  affected  the  drift  of  the  upland  to 
slightly  greater  depths  than  that  of  the  plain.  Usually  the  uppermost 
zone  of  one  or  two  feet,  colored  by  decayed  vegetable  matter  and  much 
oxidized  mineral  matter,  is  defined  as  the  soil.  The  somewhat  oxidized, 
leached  and  loosened  zone  below  the  soil  and  above  the  unmodified 
drift  is  known  as  the  sub-soil. 

Unfortunately  there  is  no  exposure  known  in  this  region,  that  goes 
down  to  bed  rock,  showing  the  relation  of  the  unmodified  drift  to 
the  underlying  rock  formation.  Judging  from  well  data  within  the 
region  and  from  exposures  in  the  surrounding  territory,  we  may,  how- 
ever, infer  that  if.  such  exposure  were  made,  the  conditions  would 
be  as  shown  in  Fig.  8.  The  drift  would  be  sharply  defined  from  the 
bed  rock.  The  surface  of  the  rock  would  undoubtedly  show  signs  of 
glacial  action  such  as  striations,  grooving  and  polishing.  In  regions 
not  invaded  by  ice  the  relations  are  very  different.  In  such  regions 
the  soil  is  derived  directly  from  the  disintegration  of  the  rock  at  the 
surface  and  is  known  as  residual  soil.  There  is  a  gradual  gradation 
from  the  soil  into  the  sub-soil  and  downward  through  the  less  and 
less   decomposed  material  to  the  unmodified  bed   rock,   as   shown   in 

Most  rock  is  more  or  less  variable  in  composition  and  texture  and 
therefore  some  parts  yield  more  readily  than  others  to  the  agents  of 
weathering.  The  result  is  differential  weathering,  with  the  soil  thicker 
at  some  places  than  at  others.  The  sandy  and  gravelly  soils  found  at 
some  places  in  the  southeast  and  northeast  portions  of  the  area  are 
beach  formations  and  were  described  in  connection  with  the  lake  plain. 

Farms. — In  the  southern  portion  of  the  region,  the  lowlands  between 
the  ancient  beaches  are  largely  used  as  truck  farms.  These  areas 
were  lagoons  during  certain  stages  in  the  retreat  of  the  lake  waters 
and  from  the  abundance  of  decaying  vegetable  matter  in  such  places 
came  to  have  rich  soils.  The  tendency  of  late  has  been  to  cover  large 
portions  of  these  lagoons  with  hot-houses  (Plate  XIV)  and  to  raise 
vegetables  for  the  Chicago  and  North  Shore  markets  at  all  seasons  of 
the  year. 

The  rolling  upland  is  excellent  farm  land.  Over  most  of  the  moraine 
belt  there  is  a  loamy  deposit  several  inches  thick  that  is  easily  tilled 
and  is  very  productive.  Between  Waukegan  and  Beach  and  extending 


92  THE   EVANSTON-WAUKEGAN    REGION.  Ibtjll.  7 

somewhat  farther  north  there  is  a  narrow  four-foot  bed  of  peaty  ma- 
terial that  is  exceedingly  rich  soil  and  might  be  used  for  lawn  or  field 
dressing.  The  deposit  is  just  west  of  the  bluff  which  borders  the  rail- 
road. Associated  with  the  peat  there  is  some  bog  iron  ore  but  not  in 
sufficient  quantity  to  be  of  commercial  value. 

Suburban  and  Summer  Homes. — The  ravine  country  east  of  the 
railroad  between  Winnetka  and  North  Chicago  is  largely  devoted  to 
suburban  and  summer  homes.  Its  eastern  margin  borders  the  lake, 
and  has  lost  much  by  the  encroachment  of  the  waves.  In  1897  Mr. 
Leverett  published  the  following  statement.*  "The  rate  at  which  the 
lake  bluff  is  being  encroached  upon  by  wave  action  has  become  a  matter 
of  much  concern  to  the  residents.  It  is  estimated  by  old  settlers  that 
from  Waukegan  to  Evanston  there  has  been,  during  the  thirty  years 
from  i860  to  1890,  a  strip  about  150  feet  in  width,  undermined  and 
carried  into  the  lake.  This  amounts  to  about  500  acres,  representing 
at  present  valuation  nearly  one  million  dollars'  worth  of  property.,, 

The  Former  Village  of  St.  Johns. — In  1845  and  for  about  ten  years 
following  there  was  a  village  located  in  the  southeast  corner  of  what 
is  now  the  Fort  Sheridan  grounds.  This  village  was  known  as  St. 
Johns.  The  chief  industry  was  brick  making,  the  yards  employing  as 
many  as  eighty  men.  A  portion  of  the  brick  yard  (Plates  II,  Fig.  A, 
and  XI)  may  now  be  seen  and  the  boundaries  of  the  kilns  may  be 
identified.  In  1858  the  railroad  built  a  spur  to  the  brick  yards  and 
the  old  railroad  grade  may  be  easily  followed  northeastward  through 
the  village  of  Highwood  into  the  Fort  Sheridan  grounds.  North  of 
the  clay  pit  remnants  of  a  foundation  and  of  an  orchard  are  at  the 
very  margin  of  the  lake  cliff.  Reports  differ  as  to  the  amount  of  land 
that  has  been  cut  away  at  this  point,  but  all  agree  that  it  was  more 
than  100  feet.  Some  old  settlers  insist  that  300  to  400  feet  have  been 
removed,  and  that  the  wearing  away  of  the  land  caused  the  site  to  be 
abandoned.  The  orchard  trees  (Plate  XIV,  Fig.  B)  at  the  edge  of 
the  cliff  and  even  overhanging  are  reported  by  some  to  have  been  in 
the  yard  to  the  west  of  the  westermost  house  in  the  village.  If  this  is 
true,  the  entire  site  of  the  village  of  St.  Johns  is  east  of  the  present 
shore  line. 

The  Economic  Uses  of  the  Glacial  Material. — The  clay  brought  to 
this  region  by  the  glacier  has  been  used  in  the  manufacture  of  brick 
at  several  places.  The  manufacture  of  brick  at  St.  Johns  has  been 
referred  to.  A  few  years  ago  brick  was  made  at  Spauldings,  three 
miles  west  of  Waukegan,  and  at  North  Chicago.  The  beach  gravels 
are  used  in  concrete  work,  for  roofing  and  as  road  material.  Large 
quantities  oT  a  fine  grade  of  gravel,  torpedo  gravel,  are  used  in  concrete 
and  at  Waukegan  in  the  manufacture  of  ready  roofing  material.  The 
glacial  bowlders  are  sometimes  used  very  artistically  in  foundations 
or  in  chimneys,  fences  or  gate  posts  (Plate  XIII,  Fig.  B). 


*  Pleistocene  features  and  deposits  of  the  Chicago  Area,  Bull.  II,  Geol.  and  Nat.  Hist.  Sur. 
of  the  Chicago  Academy  of  Sciences. 


atwood.]  GEOGRAPHIC   CONDITIONS   AND    SETTLEEENT.  93 

Rainfall* — Illinois  is  one  of  the  most  favored  of  the  west-central 
states  in  the  matter  of  rainfall.  A  deficiency  of  rainfall  has  never 
been  so  serious  as  to  cause  a  complete  failure  of  any  crop  over  a  great 
part  of  the  State,  such  as  the  less  humid  states  of  the  West  and  North- 
west have  experienced.  Its  greatest  danger  lies  in  a  deficiency  between 
June  and  September,  there  being  many  years  when  the  corn  and  other 
crops  which  ripen  in  autumn  are  shortened  by  drought  at  that  season. 
Often  heavy  rains  and  low  temperature  from  April  to  June  keep  the 
ground  cold  and  damp ;  then  a  reversal  of  conditions  suddenly  occurs 
and.  the  ground  becomes  baked  by  the  hot,  dry  atmosphere  and  blazing 
sun. 

The  average  rainfall  for  Illinois  is  distributed  as  follows :  Spring, 
10.2  inches;  summer,  11.2  inches;  autumn,  9  inches;  winter,  J.J  inches; 
giving  an  annual  precipitation  of  38.1  inches.  The  range  in  the  rain- 
fall at  Chicago  for  the  years  1867  to  1895,  inclusive,  was  23.4  inches, 
the  lowest  annual  rainfall  being  22.4  inches  in  1867  and  the  highest 
45.8  inches  in  1883.  In  general,  an  annual  precipitation  of  less  than 
25  inches  results  unfavorably  to  crops  in  Illinois,  but  this  depends  very 
largely  upon  its  seasonal  distribution.  A  year  of  30  inches  or  more  of 
rainfall  at  a  given  station  may  have  a  more  prolonged  and  serious 
drought  in  the  growing  season,  than  one  with  but  24  inches. 


*  Quoted  from  Alden  in  the  Chicago  Polio,  U.  S.  Geol.  Survey.  For  additional  information 
relative  to  the  rainfall  in  Illinois  see  Mr.  Leverett's paper  on  the  '  'Water Resources  of  Illinois" 
in  the  17th  Ann.  Rep.  U.  S.  Geol.  Surv.  Part  II.  Also  "The  Illinois  Glacial  Lobe,"  Mongr. 
XXXVIII.  U.  S.  Geol.  Surv..  Chapters  XII.  XIII.  XIV. 


94  THE    EVANSTON-WAUKEGAN    REGION.  [bdll.  7 


APPENDIXES. 


Bibliography. 

1868.  Geology  of  Cook  County,  by  H.  M.  Bannister;  Geol.  Surv.  Illinois, 
Vol.  Ill,  Geology  and  Palaeontology,  pp.  239-256,  Springfield,  1868. 

1868.  Report  on  the  Survey  of  the  Illinois  River,  by  James  A.  Wilson  and 
William  Gooding;   Rept.  Chief  Eng.,  U.  S.  A.,  1868,  p.  438. 

1878.  The  North  American  Lakes  Considered  as  Chronometers  of  Post- 
Glacial  Time,  by  Dr.  Edmund  Andrews;  Trans.  Chicago  Acad.  Sci.,  Vol.  II, 
Article  1,  pp.  1-24. 

1877.  Geology  of  Eastern  Wisconsin,  by  T.  C.  Chamberlin;  Geol.  Surv.  of 
Wis.,  Vol.  II,  1873-77,  pp.  219-233. 

1884.  Microscopic  Organisms  in  the  Bowlder  Clays  of  Chicago  and  Vicin- 
ity, by  H.  A.  Johnson  and  B.  Thomas;  Bull.  Chicago  Acad.  Sci.,  Vol.  I,  No.  4. 

1886.  Chicago  Artesian  Wells,  on  Their  Structure  and  Sources  of  Supply, 
by  Leander  Stone:     Bull.  Chicago  Acad.  Sci.,  Vol.  I,  No.  8. 

1888.  Raised  Beaches  at  the  Head  of  Lake  Michigan,  by  Frank  Leverett: 
Trans.  Wisconsin  Acad.  Sci.,  Vol.  VII,  1883-87,  pp.  177-192. 

1889.  Water  Supplies  of  Illinois  in  Relation  to  Health,  by  L.  E.  Cooley: 
Rept.  State  Board  of  Health,  Springfield,  1889. 

1890.  Lake  and  Gulf  Waterway,  by  L.  E.  Cooley.     Private  publication. 
1890.     Survey  of  Waterway  from  Lake  Michigan  to  the  Illinois  River  at 

LaSalle,  111.,  by  Capt.  W.  L.  Marshall,  U.  S.  Eng.:  Ann.  Rept.  Chief  of  En- 
gineers to  the  Secretary  of  War,  1889,  Part  3,  Appendix  JJ,  pp.  2399-2574. 

1894.  The  Ancient  Outlet  of  Michigan,  by  W.  M.  Davis:  Pop.  Sci. 
Monthly,  Vol.  XLVT,  1894,  pp.  218-229. 

1894.  Currents  of  the  Great  Lakes  as  Deducted  from  the  Movements  of 
Bottle  Papers  During  the  Seasons  1892  and  1893,  by  Mark  W.  Harrington: 
Weather  Bureau  Bulletin  B,  U.  S.  Dept.  Agriculture,  1894. 

1894.  The  Geological  Survey  of  the  Great  Lakes,  by  Dr.  J.  W.  Spencer: 
Proc.  Am.  Assoc.  Adv.  Sci.,  Brooklyn  Meeting,  1894,  pp.  242-243. 

1896.  The  Water  Resources  of  Illinois,  by  Frank  Leverett:  Seventeenth 
Ann.  Rept.  U.  S.  Geol.  Survey,  Pt.  II,  1896,  pp.  695-849. 

1897.  The  Pleistocene  Features  and  Deposits  of  the  Chicago  Area,  by 
Frank  Leverett:  Chicago  Acad.  Sci.,  Bull.  II.  Geol.  and  Nat.  Hist.  Surv., 
1897. 

1897.     A  Short  History  of  the  Great  Lakes,  by  Frank  B.  Taylor:     Studies 
in  Indiana  Geography,  Terre  Haute,  1897. 
^r^"  1897.     Modification  of  the  Great  Lakes  by  Earth  Movement,  by  G.  K.  Gil- 
bert:    Nat.  Geog.  Mag.,  Vol.  VIII,  1897,  pp.  233-247. 

1897.     The  Age  of  the  Great  Lakes  of  North  America — A  Partial  Biblio- 
graphy, by  Alex.  N.  Winchell:      Am.  Geologist,  Vol.  XIX,  1897,  pp.  336-338. 
1899.     The  Geography  of  Chicago  and  Its  Environs,  by  Rollin  D.  Salisbury 
^and  William  C.  Alden:     Bull.  No.  1,  Geog.  Soc.  Chicago,  1899. 

1899.  The  Illinois  Glacial  Lobe,  by- Frank  Leverett:  Mon.  U.  S.  Geol. 
Survey,  Vol.  XXXVIII,  1899,  pp.  339-459. 

•  1901.     Plant  Societies  of  Chicago  and  Vicinity,  by  H.  C.  Cowles:     Bull.  No. 
2,  Geog.  Soc.  of  Chicago. 

1906.  Correlation  of  the  raised  beaches  on  the  west  side  of  Lake  Michigan, 
by  J.  W.  Goldthwait:      Jour.  Geol.,  Vol.  14,  pp.  411-424. 

1907.  Abandoned  shore-lines  of  eastern  Wisconsin,  by  J.  W.  Goldthwait: 
Wis.  Geol.  and  Nat.  Hist.  Surv.  Bull.,  No.  XVII. 


ATWOOD-GOLDTHWA1T.  ]  APPENDIX.  95 


Field  Trips. 

For  the  Study  of  Ravines  and  Valleys — 

1.  Dead  river  between  Waukegan  and  Beach. 

2.  Little  Fort  river,  Waukegan. 

3.  Pettibone  creek,  North  Chicago. 

4.  Near  Glencoe. 

5.  Near  Ravinia. 

6.  Near  County  Line  station  on  the  Chicago  &  Milwaukee  Electric  railway 

7.  At  Beck's  crossing,  north  of  Glencoe. 

For  the  Study  of  Shore  Features — 

1.  Winnetka. 

2.  Ft.  Sheridan. 

3.  South  of  Pettibone  creek. 

For  Study  of  Old  Beaches — 

1.  From  Evanston  Lighthouse  west  on  Central  street. 

2.  At  Winnetka. 

3.  From  Waukegan  north  to  State  line. 

For  Study  of  Dunes — 

1.  Rogers  Park  near  Calvary  cemetery. 

2.  North  of  Waukegan  on  lowland. 

3.  On  beach  between  Lake  Bluff  and  North  Chicago. 


96  INDEX.  [bull.  7 


INDEX. 


Page. 

A. 

Abandoned  lake   shore  lines 37 

Absorbing  areas  of  aquifers 87 

Agents  at  work  on  shore  lines 29 

Aggradation 77 

Alden,  W.   C,  cited 23,   55,   56,   58.  93 

Alden,   W.   C,   Salisbury,   R.   D.,   and,   cited 33 

Algonquin    stage • 64 

Altitude    of   St.    Peters   sandstone 88 

Andrews,    Dr.    Edmund,    cited 48,  62 

Artesian     wells •  • 16,  85 

Atwood,   W.   W.,   cited 69 

Development   of   the   Ravines •  • 69 

General    Geographic    Features 1 

Geographic    Conditions   and    Settlement 89 

The    Geological    Formations  •  • 4 

Underground     Water 85 

Atwood,  W.  W.,  and  J.  W.  Goldthwait,  Physical  Geography  of  the  Evanston-Wau- 

kegan    Region 1 

B. 

Barriers    36 

Barrington,    Moraine    near 14 

Bars 38 

Basalt   in    drift •  • 18 

Base  level    in   streams 72 

Plains     •  • 75 

Beach    ridges 35 

Beach    Station,    beach    ridges   at •  • 68 

Beach    Station,    Calumet   beach    at 63 

Bed    rock •  • 16 

In  outlet  of  Glenwood   lake 56 

Of    region •  • 4,     5 

Bibliography     94 

Booth's    well •'• 16,  85 

Bowlder    clay 20 

Definition     •  • 4 

Bowlders,    largest    in    drift 19 

Uses     of •  • 92 

Brick     clays 92 

C. 

Calumet    atlas    sheet 1 

Stage •• 37,    47,  60 

Terrace     81,  82 

Calvary,    gravel    pit    at •  • 66 

Camp    Logan,    lake   plain    at 3 

Streams     near •  • 79,  83 

Canada,   drift   from 6 

Cary,    near    moraine >  • 14 

Chamberlin,   T.   C,   cited 60 

Changes   in    shore   profile •  • 32 

Characteristics   of   valleys 76 

Chert   in   drift l 18 

Chesapeake  Bay,  a  depressed  area 46 

Chicago,    atlas    sheet 1 

Academy  of  Science,  acknowledgements  to 16,  23,  48,  50,  92 


INDEX.  97 

Index — Continued. 

1    PAGE). 

Artesian     wells  •  • 85 

Rock    exposures    in 5 

Chicago   &    Northwestern    Railroad 2,    3  23 

"Chicago"     region    defined 1 

Chicago     river 3 

Topgraphy    near    head 23 

Cincinnati  shale  in  deep  wells 86 

Clay     of     region 4 

Clays    92 

Coastal     topography 32,  50 

Colorado    canyon 75 

Conglomerate    in    drift •  • 18 

Constitution    of    drift    in    area 18 

Till     .  .  •  • 20 

Continental    glaciers 6 

Cooley,    Lyman,    acknowledgements    to 23 

Corn  Products  Refining  Company,  artesian  well 85 

Course  of  a  valley 70 

Cross-section  of  ice  sheet 7 

Culver's     well 85 

Currents  along  shore 32 

Cycles    of    erosion 73 

Cycle   of  shore  processes •  • 45 


D. 

Dead    river,    flood    plain    of 79,  83 

Deflected    streams    near    Waukegan 40 

Deposition    hy    ice 13 

Streams     •  • 79 

Deposits   of  glaciers 17 

Desor,    Edward,    cited 44 

DesPlaines    atlas    sheet 1 

River     3 

Valley   at  Gflenwood   stage 58 

Development   of   coastal   topography •-....  32 

Development  of  the  Ravines    (by  W.   W.   Atwood) 69 

Direction    of   glacial    movement-  • 5 

Glacial     striae 4 

Ice     movement •  • 16 

Distribution     of    drift 20 

Drainage    of    area  •  • 3 

Drift    covered    area 26 

Driftiess    area -  - 26 

Drift     20 

Material,    sources    of  •  • 5 

Of    region 4 

Driftiess    areas 10,  17 

Drainage     of •  • ■. 26 

Topography     of 27 

Drowned    valleys 63 

Dunes     44,  51 

Durkin's    wall-  • l 16 


E. 

Effect  on   topography  of  ice 10 

Movement     •  • 17 

Erosion     cycles 73 

Erosion    of    lake    shore 28,    48,  92 

Erosive  work   of  ice 10 

Evanston,    atlas    sheet 1 

Beach    ridges     in •  • 37 

City     well 88 

Coastal     topography 50 

Peat    at 65 

Shore    erosion    at •  • 48 

Shore    line    at 3 

Evolution   of  shore   line 28 

Extent    of    area •  • 1 

Extinct     lakes 54 


-7  G 


.98  INDEX.  [bull.  7 

Index — Continued. 
f. 

Page. 

Farms    in    region 91 

Farwell's     well .  . 16,  87 

Fenneman,   N.    M.,   acknowledgements   to 29 

Ferry's     well •  • 16 

Field    trips,    suggestions    for 95 

Flint    in    drift •• 18 

'Fluctuations    in    lake    level 68 

Formation   of  an  ice   sheet •  • 6 

Terminal     moraines 23 

Former   village   of    St.    Johns ••....  92 

Foster    and    Whitney    quoted 44 

Fresh    water    shells •  • 63 


Gabbro    in    drift 18 

Galena-Trenton    in    deep    wells 86,  88 

Geographic   Conditions  and   Settlement    (by   W.   W.    Atwood) 89 

Features  of  the  Region    (by  W.  W.   Atwood) 1 

Geological    Formations    (by   W.    W.    Atwood)  .  . .  .' 4 

Gilbert,   G.    K..   acknowledgements   to •  •  .  .  .  29 

Glacial     deposits 17 

Drift,    constitution    of 4 

Drift    in    deep    wells .  86 

Material,    uses    of 92 

Glencoe,    drift    near •  • 18 

Ground    moraine   near 23 

Large    bowlders    near ....•• 19 

(Hen   Elyn,    on    moraine 14 

Glenwood    stage 37,    45,   47,  55 

Beach     formation 25 

Goldthwait,    J.    W.,    cited 64,  84 

Records  of  the   Extinct  Lakes • 54 

The    Present    Shore    Line 28 

Goldthwait,  J.  W.,  W.  W.  Atwood,  and,  Physical  Geography  of  the  Evanston-Wau- 

kegan    Region 1 

Government    road •  • 89 

Grade    of    streams 72 

Granite    in    drift .  .  •  • 18 

Gravels     92 

Green   Bay   glacial    lobe • \  17 

Road      89 

Greenland    ice    sheets •  • 8 

Grosse   Point,  beach   ridges  at 57 

Coastal     topography ••....  50 

Dunes    near 45 

Exposures     near •  • 62 

Hooked  bar  near 47 

Road     •  • 89 

Rock     shore    at 48 

Ground     moraine .  .  •  • 20 

Waters 71,  85 

Gullies,    origin    of •  • 69 


H. 

Hanging   valleys    of    Normandy 47 

Height   of   waves •  • 29 

Highland    Park    artesian    wells 85 

Moraine     .  .  •  • 51 

Roads     90 

Well     •  • 16 

Highwood,    atlas    sheet 1 

Hinsdale,    on    moraine .  .  ■  • 14 

History     of    settlement 89 

Hooked     spit •  •  .  ., 41 

Hooks     39 

Piorizontal   configuration   of  shore  lines.  .  •  • 38 

Hudson   Bay,   an   elevated   area 46 

Center    of    glaciation •  • 9,  10 

Hyde   Park,   deposition  at 48 


INDEX.  99 

Index — Continued, 
i. 

Page. 

Ice    sheet,    formation    of 6 

Influence  of  changes  in  lake  level  on  streams 81 

Intermittent    streams 71,  72 

J. 

Jaspar     in    drift 18 

K. 

Kay.    Fred,    acknowledgements    to •  • 82 

Kenilworth,    lake    plain    at 3 

Kettle     holes •  • l 23,  24 

Knobs    and    kettles 24 


Labrador   center   of   dispersion 17 

Lagoons    along    shores  •  • 36 

Lake    Algonquin 64 

Correlation     of •  • 55 

Lake    Bluff,    drift   near 18 

Lake    Chicago  •  • 46,  54 

Glenwood     stage 25 

Lake  Forest  artesian  wells •  • 85 

Deep     wells 87 

Roads     •  • 90 

Shore    erosion    at 48 

Wells    at •  • 16 

Lake   Michigan,    deepened    by    glaciers 13 

Glacial    lobe  •  • 13,  17 

Shore     line 28 

Waters,    quality    of •  • 87 

Lake    plain    in    area 3 

Lake   side,   drift  near-  • 18 

Lake    Superior,    glacial    lobe 17 

Lake    survey    charts 48 

Lane,    A.    C,    cited 68 

Lemont,    on    moraine 14 

Length    of    waves 29 

Leverett,    Frank,    acknowledgements    to 

16,   23,    50,   55,    63,   64,   65,    86,    87,   88,    92,  93 

Limestone    in    drift 18 

Limit    of   glaciation •  • 10 

Limits   of  a  valley 72 

Lithologic   hetereogeneity  of  drift •  • 17 

Little   Dead   river,   bar   at 40 

Lloyd"s    well •  • 16 

Location    of    region 1 

Roads       •  • 89 

Long  Island,   bar   on 39 

Lower  Magnesian  limestone  in  deep  wells 86,  88 

Lynnaea    reflexa 63 

M. 

Mabrey,   F.   D..   acknowledgements   to 82 

"Marcey,   D.   Oliver,   quoted 65 

Marcy's    well 16 

Marshes •  • _, 24,    26,    36,    58,  68 

Mature   conditions   of  shore   line 53 

Modified     drift •  • 24 

Definition     4 

Mont  Clare,  plain  near 23 

Moraine  at  Highland  Park 51 

Surface     •  • 69 

Moraines     14,  20 

Morton   Grove,   gravel  ridge  at 57 

Hooked    bar    near •  • 47 

Motion   of   ice   chest 7 

Movement    of    ice •  • 16 


100  INDEX.  [BULL.   7 

Index — Continued. 

N. 

Page. 

Nature  of  materials  in  geological  formations 4 

New   England,   glaciation  in •  • 10 

New     Jersey    coast 37 

New    York    harbor •  • 42 

Niagara   limestone    in    deep   wells 86 

Of    region 5 

Niles   center   and   plain •  • 57 

Nipissing    great    lakes 55 

Shore    lines 66 

Terraces     : 50,  82 

Normandy,    hanging    valleys    of 47 

North  American  ice  sheet •  • 9,   10,  11 

North  Chicago,  assorted  drift  near 5 

North     Shore 1 

"North    Shore"    region    defined 1 

Northwestern  University  Campus,  beach  ridges  on 36,  51,  65.  66 

Norwood   Park,    shore   lines •  • 58 

O. 

Oak  Park,  hooked  spit  at 58 

Origin   of  continental   glaciers •  • 6 

Origin    of    a    gully 69 

P. 

Peat 63,     65,  92 

Peat     bogs* •  • 36 

Peneplains     75 

Pettibone    Creek 82 

Assorted    drift    near 5 

Bar     at •  • 39.  40 

Flood    plain    of 79 

Intermediate    age     of •  • 78 

Large    bowlders    near ' 19 

Physa    elliptica •  • 63 

Physical   Geography    of   the   Evanston-Waukegan    Region    (by   W.    W.    Atwood    and 

J.     W.     Goldthwait) 1 

Physical    heterogeneity    of    drift.  , 18 

Pisidium,     sp •  • 63 

Planorbis     bicannatus 63 

Parvus     •  • 63 

Trivalvus 63 

Porphyry   in  drift •  • 18 

Potdam   sandstone   in   deep  wells 86.  88 

Present  shore  line  of  area •  • 28 

Price   of   topographic   maps 1 

Profile    of    equilibrium •  • 33 

Shore,    changes    in 32 

Tyrite    in    drift •  • 18 

Q. 

Quality    of    waters 87 

Quartz    in    drift •• 18 

Quartsite    in    drift 18 

R. 

Rainfall    in    area 93 

Rate  of  erosion  along  lake 48 

Ravines,   development    of 69 

Ravinia,   shore   near •  • 78 

Wells    at 16 

Records  of  the  Extinct  Lakes   (by  J.  W.   Goldthwait) •  •': 54 

Red  clays  of  Gienwood  stage. 56 

Region    discussed .....•• 1 

Rejuvenation  of   streams SO 

Residual  soils,  formation  of ••.... l 27 

Ridge    Avenue,    Evanston 37,    39,  62 

Ridge     Road •  • 89 

Riverside,    atlas    sheet 1 


INDEX.  101 

Index — Continued. 

Page. 

Road   location   in    region •  • 89 

Roads    at    Highland    Park ; . 90 

Lake    Forest : 90 

Zion     City •  • 90 

Rock    exposures    in    Chicago : 4 

In    lake    bottom 48 

Rockaway    Beach 41 

Rogers    Park,    coastal    toopography •  • 50 

Hooked    spit    near 43,  62 

Lake  bottom  at 48 

Rose    Hill    barrier 62 

Run     off •• . 69 


St.     Johns 92 

St.  Peter  sandstone,  altitude  of •  • 88 

In    deep    wells 86 

Salisbury,    R.    D.,    cited •  • 59,  69 

And   Alden,    W.    C,    cited . 33 

Sands     •  • 92 

Sandstone    in    drift 18 

Sandy    Hook 42 

Schist    in    drift • 18 

Scratched    pebbles 4 

Sea    cliff •  • 33 

Seepage 85 

Settlement    of    region 89 

Shells  in  Calumet  beach  sands • . .  63 

Shore    current . 32 

Cycle      •  • : ....:.:.......:...  45 

Shore   line   of  area 28 

Elevation     •  • 46 

Through     area 3 

Shore     terrace •  • 34 

Shores    of   Glenwood    stage 56 

Skokie     marsh • 58 

Slope   of   lake   shore 48 

Soils     of     region .  .  . 90 

South   Evanston   artesian   well 85 

Sources    of    drift    material 5 

Southern    limit    of    drift 10 

Spermaceti     cave 43 

Spits 38 

Stages  of  valley  development , 76 

Stopping    of    shore    line 60  • 

Stony    Brook    harbor ...  40 

Stratified     drift 24 

Striae    on    rock 7 

Structure     of    region 5 

Submerged     terraces 48 

Suburban     homes 92 

Subglacial     till 20 

Suggested    field    trips 95 

Summer    homes 92 

Swift's    well 16,  85 

Syenite    in    drift 18 

T. 

Taylor,    F.   B.,   acknowledgements   to 55,    64.  67 

Temporary     streams 71,  72 

Terminal     moraines 20,  23 

Terrace    along    shore 34 

Of   Calumet  stage 81 

Of    erosion 48 

Ten    fathom 48 

Of    Toleston    stage 81,  82 

Till     20 

Definition     of 5 

Toleston     stage 37.  63 

Terrace     81 

Topographic  forms  of  stream  deposits 79 

Topography    of    coast 32,  50 

Drift  covered   areas 23 

Terminal     moraines 24 

Towns    of   region 90 


102  INDEX.  [BULL. 

Index — Concluded. 

Page. 

Transportation    by     streams 79 

Trenton,    in    deep    wells 86 

Tributary     valleys 70 

Truck  farms   on   lowlands 91 

U. 

Underground  Water   (by  W.  W.  Atwood) 85 

Undertow     31 

Unglaciated   areas,    topography    of 27 

United    States   Geological    Survey,    acknowledgements    to 

9,   16,   23,   29,  39,   56,  60,  87,  93 

Topographic    maps    of 1 

Upland     area 2 

V. 

Valleys,     courses    of 70 

Valparaiso     moraine 14 

Villages    of   region 90 

W. 

Walker,    Bryant,    acknowledgements    to 63 

Wastage   of   ice   sheet 8 

"Washes"     69 

Waukegan,    artesian    wells 85 

Atlas     sheet 1 

Beach    features    at 68 

Beach    ridges    at 60 

Coastal    topography 51.  52 

Deflected    streams    near 40 

Ground    moraine    near 23 

Igneous    rock    near 19 

Shore    erosion    at 48 

Shore    line    at 3 

Slope   of   shore  at 48 

Water     supply 86 

Wells    at 16 

Waves     29 

Wells    reaching    bed    rock 16 

West    Meadow    Beach 39 

Westerfield,   C.   P..   acknowledgements   to 89 

Wilmette,     embayment 42.  02 

Government     road     at 89 

Lake    plain    at 3 

Winnetka,    coastal    topography 50,  51 

Highland     near 2 

Lake   plain    at 3 

Ridge    near 23 

Shore    erosion    at 48 

Wells    at 16 

Winthrop    Harbor   beach    ridges 60 

Exposure     near 25 

Lake    plain    at 3 

Work    of    continental    glaciers 6 

Glacier    ice 10 

Wisconsin   Geological   and   Natural    History    Survey,    acknowledgements    to 

6,    26,    29,    64,  69 

Y. 

Yield    of    artesian    wells 87 


Zion  City,   beach   ridges  at 60 

Calumet    beach    at 63 

Coastal     topography 52 

Lake   plain    at 5 

Roads     89 

Sand    ridges    at 68 

Slope    off    shore    at 48 


LIBRARY  CATALOGUE  SLIPS. 


[Mount  each  slip  upon  a  separate  card,  placing  the  subject  at  the  top  of /the  second  slip.  The 
name  of  the  series  should  not  be  repeated  on  the  series  card,  but  the  additional  numbers 
should  be  added,  as  received,  to  the  first  entry.] 


Author. 


Subject. 


Series 


Atwood,  Wallace  W.,  and  James  Walter  Goldthwait 

Physical  Geography  of  the  Evanston-Waukegan   Re- 
gion.    Urbana,  University  of  Illinois,  1908. 

(102  pp.  48  fig.  14  pi.)    State  Geological  Survey.    Bulletin  No.  7. 


Goldthwait,  James  Walter,  and  Wallace  W.  Atwood 

Physical  Geography  of  the  Evanston-Waukegaii  Re- 
gion.    Urbana,  University  of  Illinois,  1908. 

(102  pp.  48  fig.  14  pi.)    State  Geological  Survey.    Bulletin  No.  7. 


Wallace  W.  Atwood  and  James  Walter  Goldthwait 

Physical  Geography  of  the  Evanston-Waukegan  Re- 
gion.    Urbana,  University  of  Illinois,  1908. 

(102  pp.  48  fig.  14  pi.)    State  Geological  Survey.    Bulletin  No.  7. 


State  Geological  Survey. 

Bulletins.        No.    7.        W.   W.    Atwood   and  J.   W 
Goldthwait.     Physical  Geography  of   the  Evanston-Wau- 
kegan Region. 


NOTICE. 

A  portion  of  each  edition  of  the  Bulletins  of  the  State  Geological  Survey  is 
set  aside  for  gratuitous  distribution.  To  meet  the  wants  of  libraries  and  in- 
dividuals not  reached  in  this  first  distribution,  500  copies  are  in  each  case 
reserved  for  sale  at  cost,  including  postage.  The  reports  may  be  obtained 
upon  application  to  the  State  Geological  Survey,  Urbana,  Illinois,  and  checks 
an  money  orders  should  be  made  payable  to  H.  Foster  Bain,  Urbana. 

The  list  of  publications  is  as  follows: 

Bulletin  1.  The  Geological  Map  of  Illinois:  by  Stuart  Weller.  Including  a 
folded,  colored  geological  map  of  the  State  on  the  scale  of  12  miles  to  the 
inch,  with  descriptive  text  of  26  pages.  Gratuitous  edition  exhausted.  Sale 
price  45  cents. 

Bulletin  2.  The  Petroleum  Industry  of  Southeastern  Illinois;  by  W.  S. 
Blatchley.  Preliminary  report  descriptive  of  condition  up  to  May  10th,  1906. 
109  pages.     Gratuitous  edition  exhausted.     Sale  price  25 cents. 

Bulletin  3.  Composition  and  Character  of  Illinois  Coals;  by  S.  W.  Parr; 
with  chapters  on  the  Distribution  of  the  Coal  Beds  of  the  State,  by  A.  Bement, 
and  Tests  of  Illinois  Coals  under  Steam  Boilers,  by  L.  P.  Breckenridge.  A 
preliminary  report  of  86  pages.  Gratuitous  edition  exhausted.  Sale  price 
25  cents. 

Bulletin  4.  Year  Book  for  1906,  by  H.  Foster  Bain,  director,  and  others.  In- 
cludes papers  on  the  topographic  survey,  on  Illinois  fire  clays,  on  limestones 
for  fertilizers,  on  silica  deposits,  on  coal,  and  on  regions  near  East  St.  Loui?, 
Springfield  and  in  southern  Calhoun  county.    260  pages.    Postage  9  cents. 

Bulletin  5.  Water  Resources  of  the  East  St.  Louis  District;  by  Isaiah 
Bowman,  assisted  by  Chester  Albert  Reeds.  Including  a  discussion  of  the 
topographic,  geologic  and  economic  conditions  controlling  the  supply  of  water 
for  municipal  and  industrial  purposes,  with  map  and  numerous  well  records 

and  analyses.     128  pages,  postage  6"  cents. 

Bulletin  6.  The  Geological  Map  of  Illinois;  by  Stuart  Weller.  Second 
edition.  Including  a  folded  colored  geological  map  of  the  State  on  the  scale 
of  12  miles  to  the  inch,  showing  the  distribution  of  the  formations  and  the 
location  of  coal  mines,  oil  pools,  lead,  zinc  and  fluorspar  mines,  with  de- 
scriptive text  of  32  pages.  Gratuitous  edition  exhausted    Sale  price  '/5  cents. 

Bulletin  7.  Physical  Geography  of  the  Evanston-Waukegan  Region;  by 
Wallace  W.  Atwood  and  James  Walter  Goldthwait.  Forming  the  first  of 
the  educational  bulletins  of  the  survey  and  designed  especially  to  meet  the 
needs  of  teachers  in  the  public  schools.    102  pages.     Postage  6  cents. 

Circular  No.  1.  The  Mineral  Production  of  Illinois  in  1905.  Pamphlet,  14 
pages,  postage  2  cents. 

Circular  No.  2.  The  Mineral  Production  of  Illinois  in  1906.  Pamphlet,  16 
pages,  postage  2  cents. 


